Muscles around the hip

Muscles of the Thigh

Glossary

adductor brevis muscle that adducts and medially rotates the thigh adductor longus muscle that adducts, medially rotates, and flexes the thigh adductor magnus muscle with an anterior fascicle that adducts, medially rotates and flexes the thigh, and a posterior fascicle that assists in thigh extension anterior compartment of the leg region that includes muscles that dorsiflex the foot anterior compartment of the thigh region that includes muscles that flex the thigh and extend the leg biceps femoris hamstring muscle calcaneal tendon (also, Achilles tendon) strong tendon that inserts into the calcaneal bone of the ankle dorsal group region that includes the extensor digitorum brevis extensor digitorum brevis muscle that extends the toes extensor digitorum longus muscle that is lateral to the tibialis anterior extensor hallucis longus muscle that is partly deep to the tibialis anterior and extensor digitorum longus femoral triangle region formed at the junction between the hip and the leg and includes the pectineus, femoral nerve, femoral artery, femoral vein, and deep inguinal lymph nodes fibularis brevis (also, peroneus brevis) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints fibularis longus (also, peroneus longus) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints fibularis tertius small muscle that is associated with the extensor digitorum longus flexor digitorum longus muscle that flexes the four small toes flexor hallucis longus muscle that flexes the big toe gastrocnemius most superficial muscle of the calf gluteal group muscle group that extends, flexes, rotates, adducts, and abducts the femur gluteus maximus largest of the gluteus muscles that extends the femur gluteus medius muscle deep to the gluteus maximus that abducts the femur at the hip gluteus minimus smallest of the gluteal muscles and deep to the gluteus medius gracilis muscle that adducts the thigh and flexes the leg at the knee hamstring group three long muscles on the back of the leg iliacus muscle that, along with the psoas major, makes up the iliopsoas iliopsoas group muscle group consisting of iliacus and psoas major muscles, that flexes the thigh at the hip, rotates it laterally, and flexes the trunk of the body onto the hip iliotibial tract muscle that inserts onto the tibia; made up of the gluteus maximus and connective tissues of the tensor fasciae latae inferior extensor retinaculum cruciate ligament of the ankle inferior gemellus muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip lateral compartment of the leg region that includes the fibularis (peroneus) longus and the fibularis (peroneus) brevis and their associated blood vessels and nerves medial compartment of the thigh a region that includes the adductor longus, adductor brevis, adductor magnus, pectineus, gracilis, and their associated blood vessels and nerves obturator externus muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip obturator internus muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip patellar ligament extension of the quadriceps tendon below the patella pectineus muscle that abducts and flexes the femur at the hip pelvic girdle hips, a foundation for the lower limb piriformis muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip plantar aponeurosis muscle that supports the longitudinal arch of the foot plantar group four-layered group of intrinsic foot muscles plantaris muscle that runs obliquely between the gastrocnemius and the soleus popliteal fossa diamond-shaped space at the back of the knee popliteus muscle that flexes the leg at the knee and creates the floor of the popliteal fossa posterior compartment of the leg region that includes the superficial gastrocnemius, soleus, and plantaris, and the deep popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior posterior compartment of the thigh region that includes muscles that flex the leg and extend the thigh psoas major muscle that, along with the iliacus, makes up the iliopsoas quadratus femoris muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip quadriceps femoris group four muscles, that extend and stabilize the knee quadriceps tendon (also, patellar tendon) tendon common to all four quadriceps muscles, inserts into the patella rectus femoris quadricep muscle on the anterior aspect of the thigh sartorius band-like muscle that flexes, abducts, and laterally rotates the leg at the hip semimembranosus hamstring muscle semitendinosus hamstring muscle soleus wide, flat muscle deep to the gastrocnemius superior extensor retinaculum transverse ligament of the ankle superior gemellus muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip tensor fascia lata muscle that flexes and abducts the thigh tibialis anterior muscle located on the lateral surface of the tibia tibialis posterior muscle that plantar flexes and inverts the foot vastus intermedius quadricep muscle that is between the vastus lateralis and vastus medialis and is deep to the rectus femoris vastus lateralis quadricep muscle on the lateral aspect of the thigh vastus medialis quadricep muscle on the medial aspect of the thigh

MeetDr Roderick BrooksOrthopaedic Surgeon | Hip & Knee Surgery

Hip Anatomy

The hip joint is the largest weight-bearing joint in the human body. It is also referred to as a ball and socket joint and is surrounded by muscles, ligaments, and tendons. The thigh bone or femur and the pelvis join to form the hip joint.

Any injury or disease of the hip will adversely affect the joint’s range of motion and ability to bear weight.

The hip joint is made up of the following:

  • Bones and joints
  • Ligaments of the joint capsule
  • Muscles and tendons
  • Nerves and blood vessels that supply the bones and muscles of the hip

Bones and Joints

The hip joint is the junction where the hip joins the leg to the trunk of the body. It is comprised of two bones: the thigh bone or femur and the pelvis which is made up of three bones called ilium, ischium, and pubis. The ball of the hip joint is made by the femoral head while the socket is formed by the acetabulum. The Acetabulum is a deep, circular socket formed on the outer edge of the pelvis by the union of three bones: ilium, ischium and pubis. The lower part of the ilium is attached by the pubis while the ischium is considerably behind the pubis. The stability of the hip is provided by the joint capsule or acetabulum and the muscles and ligaments which surround and support the hip joint.

The head of the femur rotates and glides within the acetabulum. A fibrocartilaginous lining called the labrum is attached to the acetabulum and further increases the depth of the socket.

The femur or thigh bone is one of the longest bones in the human body. The upper part of the thigh bone consists of the femoral head, femoral neck, and greater and lesser trochanters. The head of the femur joins the pelvis (acetabulum) to form the hip joint. Next to the femoral neck, there are two protrusions known as greater and lesser trochanters which serve as sites of muscle attachment.

Articular cartilage is the thin, tough, flexible, and slippery surface lubricated by synovial fluid that covers the weight-bearing bones of the body. It enables smooth movements of the bones and reduces friction.

Ligaments

Ligaments are fibrous structures that connect bones to other bones. The hip joint is encircled with ligaments to provide stability to the hip by forming a dense and fibrous structure around the joint capsule. The ligaments adjoining the hip joint include:

  • Iliofemoral ligament – This is a Y-shaped ligament that connects the pelvis to the femoral head at the front of the joint. It helps in limiting over-extension of the hip.
  • Pubofemoral ligament – This is a triangular shaped ligament that extends between the upper portion of the pubis and the iliofemoral ligament. It attaches the pubis to the femoral head.
  • Ischiofemoral ligament – This is a group of strong fibers that arise from the ischium behind the acetabulum and merge with the fibers of the joint capsule.
  • Ligamentum teres – This is a small ligament that extends from the tip of the femoral head to the acetabulum. Although it has no role in hip movement, it does have a small artery within that supplies blood to a part of the femoral head.
  • Acetabular labrum – The labrum is a fibrous cartilage ring which lines the acetabular socket. It deepens the cavity increasing the stability and strength of the hip joint.

Muscles and Tendons

A long tendon called the iliotibial band runs along the femur from the hip to the knee and serves as an attachment site for several hip muscles including the following:

  • Gluteals – These are the muscles that form the buttocks. There are three muscles (gluteus minimus, gluteus maximus, and gluteus medius) that attach to the back of the pelvis and insert into the greater trochanter of the femur.
  • Adductors – These muscles are in the thigh which help in adduction, the action of pulling the leg back towards the midline.
  • Iliopsoas: This muscle is in front of the hip joint and provides flexion. It is a deep muscle that originates from the lower back and pelvis, and extends up to the inside surface of the upper part of the femur.
  • Rectus femoris – This is the largest band of muscles located in front of the thigh. They also are hip flexors.
  • Hamstring muscles- These begin at the bottom of the pelvis and run down the back of the thigh. Because they cross the back of the hip joint, they help in extension of the hip by pulling it backwards.

Nerves and Arteries

Nerves of the hip transfer signals from the brain to the muscles to aid in hip movement. They also carry the sensory signals such as touch, pain, and temperature back to the brain.

The main nerves in the hip region include the femoral nerve in the front of the femur and the sciatic nerve at the back. The hip is also supplied by a smaller nerve known as the obturator nerve.

In addition to these nerves, there are blood vessels that supply blood to the lower limbs. The femoral artery, one of the largest arteries in the body, arises deep in the pelvis and can be felt in front of the upper thigh.

Hip movements

All the anatomical parts of the hip work together to enable various movements. Hip movements include flexion, extension, abduction, adduction, circumduction, and hip rotation.

The hip’s unique anatomy enables it to be both extremely strong and amazingly flexible, so it can bear weight and allow for a wide range of movement.

The hip is located where the head of the femur, or thighbone, fits into a rounded socket of the pelvis. This ball-and-socket construction allows for three distinct types of flexibility:

  • Hip flexion and extension – moving the leg back and forth;
  • Hip abduction and adduction – moving the leg out to the side (abduction) and inward toward the other leg (adduction); and
  • Rotation – pointing toes inward (internal rotation) or outward (external rotation) and then moving the straightened leg in the direction of the toes.

Also known as the acetabulofemoral joint, the hip joint is comprised of these basic components:

  • Hip bones, including the femur and pelvic bones;
  • Hip articular cartilage that decreases friction between the bones and allows for a smooth gliding motion;
  • Hip muscles that both support the joint and enable movement;
  • Hip ligaments and tendons, tough, fibrous tissues that bind bones to bones and muscles to bones; and
  • Synovial membrane and fluid, which encapsulates the hip joint and lubricates it, respectively.

Hip problems occur when any one of these components starts to degenerate or is in some way compromised or irritated.

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Structure of the Hip Joint

The hip joint is constructed and functions as follows:

Hip bones

  • The hip is located where the top of the femur bone, or thighbone, fits into the pelvis.
  • The femur bone is the longest bone in the body, extending from the knee to the hip. At the top of the femur bone is the greater trochanter, that boney knob that people often refer to as their hip, and the bulbous “femoral head” which makes contact with the pelvis and forms the ball of the ball and socket joint. It is covered with articular cartilage, which serves to decrease friction.
  • The femoral head fits into the acetabulum, the round socket of the pelvic bone.

Hip articular cartilage

  • Both the femoral head and the acetabulum are lined with articular cartilage.
  • Articular cartilage is an extremely slippery, strong, flexible material that covers a bone at the site of the joint.
    • When the femoral head rotates in the acetabulum, the articular cartilage allows the two surfaces to glide against each other.
    • Articular cartilage also acts as a shock absorber, cushioning bones against impacting each other (e.g. while jumping).
    • When articular cartilage is damaged or thinned, its ability to protect against friction and impact are impeded.
    • Read more about What Is Cartilage?

  • A strong piece of cartilage, called the labrum, rings the outer edge of the acetabulum. The labrum deepens the socket joint, making the joint more stable, but its elasticity allows for flexibility.
  • Over time the smooth articular cartilage that makes up the surfaces of the hip joint may be damaged or blemished by normal wear and tear or from trauma. This process is referred to as arthritis.

Hip ligaments and tendons

  • The hip has several ligaments connecting the femur to the pelvis and tendons connecting the bones to many surrounding muscles. Tightness of these ligaments and tendons can cause hip instability and pain.
  • Strong and flexible ligaments and tendons provide structure to the hip, reducing strain on the joint, so most hip osteoarthritis therapies will including stretching and strengthening of these structures.

In This Article:

  • Hip Anatomy
  • Hip Anatomy Video

Synovial fluid

  • A synovial membrane encapsulates the entire hip joint. This membrane produces synovial fluid, a viscous substance that lubricates and circulates nutrients to the joint.
  • When the hip is at rest, the synovial fluid is stored in the cartilage, much like water in a sponge.
  • When the hip rotates or bears weight the synovial fluid is squeezed out. Therefore, joint use is necessary to keep the hip joint lubricated and healthy.
  • Small sacs of synovial fluid, called bursae (singular is “bursa”) surround all major joints, including the hip joint. Bursae help protect the muscles, bones and tendons from friction as the hip moves. When the bursae are inflamed, the condition is called hip bursitis.
  • See What Is a Synovial Joint?

Hip muscles
The hip joint is surrounded by several muscles, including:

  • Gluteal muscles, located on the back of the hip (buttocks);
  • The adductor muscle on the inner thigh;
  • The iliopsoas muscle, which extends from the lower back to upper femur;
  • Quadriceps, a group of four muscles that comprise the front of the thigh; and
  • Hamstrings, a group of muscles that comprise the back of the thigh and extend to just below the knee.

Together, these muscles support the hip joint, so exercises to relieve hip osteoarthritis symptoms will focus on these muscles as well as muscles of the core.

When the hip joint becomes inflamed and painful, the pain may be felt in the groin but may also be referred into the back, buttocks and down the front or back of the leg.

Hip Anatomy on X-Rays and Other Imaging Studies

It is important to note that the degree of anatomical problems (such as the degree of hip joint deterioration) that can be seen on a hip x-ray does not always correlate with the level of pain.

For example, a patient could have hip x-rays that show moderate right hip arthritis and mild arthritis on the left, but he or she may only have pain on the side showing mild hip arthritis.

This counterintuitive result is due to the fact that the pain felt from arthritis is usually due to inflammation in the joint and not the arthritis itself. This concept applies to all the joints in the body and is important to understand because treating the inflammation will often treat the pain and dysfunction and can often help someone put off surgery or avoid it all together.

Hip Anatomy, Function and Common Problems

The hip joint is a ball-and-socket type joint and is formed where the thigh bone (femur) meets the pelvis. The femur has a ball-shaped head on its end that fits into a socket formed in the pelvis, called the acetabulum. Large ligaments, tendons, and muscles around the hip joint hold the bones (ball and socket) in place and keep it from dislocating.

Front View of the Hip Joint Bones

Normally, a smooth cushion of shiny white hyaline (or articular) cartilage about 1/4 inch thick covers the femoral head and the acetabulum. The articular cartilage is kept slick by fluid made in the synovial membrane (joint lining). Synovial fluid and articular cartilage are a very slippery combination—3 times more slippery than skating on ice and 4 to 10 times more slippery than a metal on plastic hip replacement. Synovial fluid is what allows us to flex our joints under great pressure without wear. Since the cartilage is smooth and slippery, the bones move against each other easily and without pain.

When the cartilage is damaged, whether secondary to osteoarthritis (wear-and-tear type arthritis) or trauma, joint motion can become painful and limited.

The hip joint is one of the largest joints in the body and is a major weight-bearing joint. Weight bearing stresses on the hip during walking can be 5 times a person’s body weight. A healthy hip can support your weight and allow you to move without pain. Changes in the hip from disease or injury will significantly affect your gait and place abnormal stress on joints above and below the hip.

It takes great force to seriously damage the hip because of the strong, large muscles of the thighs that support and move the hip.

Anatomical Terms

Anatomical terms allow us to describe the body and body motions more precisely. Instead of your doctor simply saying that “the patient knee hurts”, he or she can say that “the patient’s knee hurts anterolaterally”. Identifying specific areas of pain helps to guide the next steps in treatment or work-up. Below are some anatomic terms doctors use to describe location (applied to the hip):

  • Anterior — the abdominal side (front) of the hip
  • Posterior — the back side of the hip
  • Medial — the side of the hip closest to the spine
  • Lateral — the side of the hip farthest from the spine
  • Abduction — move away from the body (raising the leg away from midline i.e. towards the side)
  • Adduction — move toward the body (lowering the leg toward midline i.e. from the side)
  • Proximal — located nearest to the point of attachment or reference, or center of the body
    • example: the knee is proximal to the ankle
  • Distal — located farthest from the point of attachment or reference, or center of the body
    • example: the ankle is distal to the knee
  • Inferior — located beneath, under or below; under surface

Anatomy of the Hip

Joint capsule of the hip

Like the shoulder, the hip is a ball-and-socket joint, but is much more stable. The stability in the hip begins with a deep socket—the acetabulum. Additional stability is provided by the surrounding muscles, hip capsule and associated ligaments. If you think of the hip joint in layers, the deepest layer is bone, then ligaments of the joint capsule, then muscles are on top. Various nerves and blood vessels supply the muscles and bones of the hip.

Bony Structures of the Hip

The hip is formed where the thigh bone (femur) meets the three bones that make up the pelvis: the ilium, the pubis (pubic bone) and the ischium. These three bones converge to form the acetabulum, a deep socket on the outer edge of the pelvis. By adulthood, these three bones are completely fused and the pelvis is effectively a single bone.

The femur is the longest bone in the body. The neck of the femur connects the femoral head with the shaft of the femur. The neck ends at the greater and lesser trochanters, which are bony prominences of the femur that various muscles attach to. The greater trochanter serves as the site of attachment for the abductor and external rotator muscles which are important stabilizers of the hip joint. This is the prominent part of your hip that you can actually feel on the outer aspect of your thigh. The lesser trochanter serves as the attachment site of the iliopsoas tendon, one of the muscles that allows you to bend your hip.

It is important to remember that the actual hip joint lies deep in the groin area. This is important, because true hip joint issues are typically associated with groin pain.

The Hip Joint

The hip joint is a ball and socket type joint. The femoral head (ball) fits into the acetabulum (socket) of the pelvis. The large round head of the femur rotates and glides within the acetabulum. The depth of the acetabulum is further increased by a fibrocartilagenous labrum that attaches to the outer rim of the acetabulum. It acts to deepen the socket and to add additional stability to the hip joint. The labrum can become torn and cause symptoms such as pain, weakness, clicking, and instability of the hip.

Bones of the Hip Joint

There are numerous structures that contribute stability to the hip:

  • The ball and socket bony structure
  • The labrum
  • The capsule and its associated ligaments: e.g. iliofemoral ligament, pubofemoral ligament
  • The surrounding muscles including the abductors (gluteus medius and minimus) and external rotators (gemelli muscles, piriformis, the obturators).

Hip Ligaments

The iliofemoral ligament in the hip

The stability of the hip is increased by the strong ligaments that encircle the hip (the iliofemoral, pubofemoral, and ischiofemoral ligaments). These ligaments completely encompass the hip joint and form the joint capsule. The iliofemoral ligament is considered by most experts to be the strongest ligament in the body. The ligamentum teres is a small tubular structure that connects the head of the femur to the acetabulum. It contains the artery of the ligamentum teres. In infants, this serves as a relatively important source of blood supply to the head of the femur. In adults, the ligamentum teres is thought by most to be more of a vestigial structure that serves little function.

The ischiofemoral ligament of the hip

Muscles of the Hip

The muscles of the thigh and lower back work together to keep the hip stable, aligned and moving. It is the muscles of the hip that allow the movements of the hip:

  • flexion – bend
  • extension – straighten
  • abduction – leg move away from midline
  • adduction – leg moves back towards midline
  • external rotation (allows for the foot to point outwards)
  • internal rotation (allows for the foot to point inward)

The hip muscles are divided up into three basic groups based on their location: anterior muscles (front), posterior (back), and medial (inside). The muscles of the anterior thigh consist of the quadriceps (or quads): vastus medialis, intermedius, lateralis and rectus femoris muscles. The quads make up about 70% of the thigh’s muscle mass. The main functions of the quads are flexion (bending) of the hip and extension (straightening) of the knee.

The gluteal and hamstring muscles, as well as the external rotators of the hip are located in the buttocks and posterior thigh. The gluteal muscles consist of the gluteus maximum, gluteus medius, and gluteus minimus. The gluteus maximus is the main hip extensor and helps keep up the normal tone of the fascia lata or iliotibial (IT) band, which is the long, sheet-like tendon on the side of your thigh. It helps with motion of the hip, but perhaps more importantly, acts to help stabilize the knee joint.

Gluteus medius and minimus are the main abductors of the hip —that is, they move the leg away from the midline of the body (using the spine as a midline reference point). They also are the main internal rotators of the hip (i.e. turn the foot inwards). The gluteus medius and minimus are also important stabilizers of the hip joint and help to keep the pelvis level as we walk.

The tensor fascia lata (TFL) is another abductor of the hip, which, along with the gluteus maximus, attaches to the IT band. The IT band is a common cause of lateral (outside) hip, thigh, and knee pain.

The medial muscles of the hip are involved in the adduction of the leg i.e. bringing the leg back towards the midline. These muscles include the adductors (adductor magnus, adductor longus, adductor brevis, pectineus, gracilis). Obturator externus also helps to adduct the leg.

The external rotator muscles (piriformis, gemelli, obturator internus) of the hip are located in the buttock area and assist in lateral rotation of the hip (out-toeing). Lateral rotation is needed for crossing the legs.

Blood Vessels and Nerves of the Hip

The sciatic nerve is located where it could get injured from a backwards dislocation of the femoral head.

Nerves carry signals from the brain to the muscles to move the hip and carry signals from the muscles back to the brain about pain, pressure and temperature. The main nerves of the hip that supply the muscles in the hip include the femoral, obturator, and sciatic nerves.

The sciatic nerve is the most commonly recognized nerve in the hip and thigh. The sciatic nerve is large—as big around as your thumb—and travels beneath the gluteus maximus down the back of the thigh where it branches to supply the muscles of the leg and foot. Hip dislocations can cause injury to the sciatic nerve.

The blood supply to the hip is extensive and comes from branches of the internal and external iliac arteries: the femoral, obturator, superior and inferior gluteal arteries. The femoral artery is well-known because of its use in cardiac catheterization. You can feel its pulse in your groin area. It travels from deep within the hip down the thigh and down to the knee. It is the continuation of the external iliac artery which lies within the pelvis. The main blood supply to the femoral head comes from vessels that branch off of the femoral artery: the lateral and medial femoral circumflex arteries. Disruption of these arteries can lead to osteonecrosis (bone death) of the femoral head. These arteries can become disrupted with hip fractures and hip dislocations.

Bursae

Bursae are fluid filled sacs lined with a synovial membrane which produce synovial fluid. Bursae are often found near joints. Their function is to lessen the friction between tendon and bone, ligament and bone, tendons and ligaments, and between muscles. There are as many as 20 bursae around the hip. Inflammation or infection of the bursa called bursitis.

The trochanteric bursa is located between the greater trochanter (the bony prominence on the femur) and the muscles and tendons that cross over the greater trochanter. This bursa can get irritated if the IT band is too tight. This bursa is a common cause of lateral thigh (hip) pain. Two other bursa that can get inflamed are the iliopsoas bursa, located under the iliopsoas muscle and the bursa located over the ischial tuberosity (the bone you sit on).

Common Problems of the Hip

Posterior Hip dislocation

  • Osteoarthritis
  • Dislocation (see image above of simple dislocation)
  • Bursitis
  • Fracture
  • Femoroacetabular impingement
  • Labral tear
  • IT band syndrome
  • Snapping hip syndrome
  • Aseptic or Avascular necrosis
  • Congenital Dislocation
  • Acetabular dysplasia
  • Coxa valga
  • Coxa vara
  • Tumor
  • Legg-Perthes disease

Surgery of the Hip

  • Hip Replacement
  • Hip arthroscopy
  • Hip fracture fixation
  • Hip preservation surgery

The hip joint is largely responsible for mobility. So any injury, trauma, or disease that affects its function can significantly reduce a person’s independence.

Lastly, there are many conditions in and around the hip and even conditions of the spine, that can cause pain in the hip area. Therefore, if you suspect that you might be having a problem with your hip(s), don’t hesitate to visit a trusted doctor for further evaluation.

Note that the information in this article is purely informative and should never be used in place of the advice of professionals.

Dr. Andrew Chung is a graduate of the Philadelphia College of Osteopathic Medicine. He is currently Spine Surgery Fellow at Keck Hospital, University of Southern California and formerly Chief Resident and an Instructor of Orthopedic Surgery in the Department of Orthopedic Surgery at the Mayo Clinic in Arizona.

A Guide to Hip Anatomy

If you are starting to feel hip pain or stiffness, you’ll want to know more about the bones and muscles that make up the hip’s anatomy.

Hip Anatomy: Bones

The hip joint is made up of two bones: the pelvis and the femur (the thighbone). It is the largest ball-and-socket joint in your body. The “ball” is the rounded end of the femur (also called the femoral head). The “socket” is a concave depression in the lower side of the pelvis (also called the acetabulum). The femoral head fits into the acetabulum to form the hip joint. This anatomy allows for a lot of motion within the joint — for instance, walking, running, and climbing.

The femoral head attaches by way of the femoral neck to the rest of the femur. At the top of the femur, next to the femoral neck, there is another bump on the outside of your hip called the greater trochante to which muscles attach. Cartilage helps prevent friction between the femoral head and the acetabulum, but hip pain can occur if your cartilage begins to wear down or is damaged.

“I see a lot of patients who have injuries to the joint, especially to cartilage,” says Brian Parsley, MD, assistant professor in the department of orthopedic surgery at the Baylor College of Medicine in Houston, Texas.

Hip Anatomy: Muscles and Tendons

The motion of the ball-and-socket is controlled by several very powerful muscles which attach to the bones. The muscles you probably know the best are your “glutes” (gluteal muscles), the large, strong muscles that attach to the back of your hip bones and comprise the buttocks.

“The glutes attach to your greater trochanter; those muscles help hold your pelvis and your body up so you don’t fall over and also help you walk,” says Dr. Parsley. “On top of that layer of muscle is the iliotibial band, which starts at the brim of your pelvis outside the hip joint and runs down your leg.”

If the iliotibial band (a long tendon that many muscles in your hip and leg attach to) becomes too tight or overused, this can contribute to hip pain.

Some of the other muscles in the hip are:

  • Adductor muscles on the inside of your thigh.
  • Iliopsoas muscle, a hip flexor muscle that attaches to the upper thigh bone.
  • Rectus femoris muscle, one of the quadriceps muscles on the front of your thigh.

Muscles play an important role in the health and well-being of your hip. All these muscles work together to provide you with range of motion in your hip while keeping your body stable and upright. “The underlying recommendation for preventing hip pain would be to try and maintain flexibility and muscle tone,” Parsley says.

Hip Anatomy: Pain Sources

General causes of hip pain include:

  • Muscle strain
  • Bone fracture (such as a fracture of the femoral neck)
  • Tendinitis
  • Arthritis
  • Bone spurs or other malformations of your hip

Parsley also sees a lot of patients with bursitis of the hips. This condition is caused when bursae, small fluid-filled sacks that act as cushions in parts of your body where there is friction between muscles, bones, and tendons, become inflamed or damaged from injury or infection.

One of the most common forms of bursitis is trochanteric bursitis (pain on the outside of your hip), but there are bursae in other parts of your hip as well. For example, there is one under the iliopsoas muscle in the front of your hip.

The hip is a complicated mechanism and therefore hip pain can originate in many different parts of the joint. Learning the anatomy of your hip will better enable you to pinpoint your pain and work with your doctor to keep it from limiting your life.

Hip – Bones, Ligaments, Muscles & Conditions

The hip joint is one of the largest joints in the body. It is composed of one osseous joint. The hip is built for weight bearing and movement in several different planes. Most of the stability of the hip is derived from the capsule, ligaments, muscle and a cartilaginous tissue called the labrum.

Bone and Joint

The hip, like the shoulder, is a ball and socket joint. It is formed by the head of the femur (thigh bone), which sits in the acetabulum, a part of pelvis. The head of the femur is large (ball) and the acetabulum (socket) is shallow. This makes the joint unstable but simultaneously allows for greater mobility.

The bony joint surfaces of the head of the femur and acetabulum are covered with articular cartilage. The articular cartilage has a smooth and shiny surface that allows the ends of the bones to slide freely over each other.

Common conditions of the hip joint are hip osteoarthritis, hip rheumatoid arthritis, hip fractures, aseptic necrosis of the hip, and hip dislocation, slipped femoral epiphysis and degenerative hip disease.

Muscles

The muscles and tendons in the hip provide stability and active movement. . The anterior muscles (iliopsoas, rectus fermoris) move the hip forward. The posterior muscles, hamstrings and luteus maximus, move the hip backward. The lateral muscles, gluteus minimus, gluteus medius, and tensor fascia latae, move the hip out to the side or abduct the leg. These muscles also stabilize the hip and pelvis when walking and running.

The muscles of the inner thigh, or adductors, function to bring the hip and leg toward the opposite leg. They are called the adductor magnus and adductor longus. The deeper muscles of the hip, or rotators, function to rotate the hip in and out. The hip rotators include the piriformis, gemellus superior, gemellus inferior, obturator internus, obturator externus, and quadratus femoris.

Common conditions of the hip muscles include hamstring strain, hamstring tear, psoas strain, adductor strain, muscle tear and piriformis syndrome.

Ligaments and Labrum

The hip joint is protected and surrounded by a soft tissue sleeve called the hip joint capsule. Ligaments, soft tissue structures that connect bone to bone, reinforce the capsule. The capsule and ligaments provide passive stability to the hip joint, but allow movements in different planes. The labrum of the hip is a fibrocartilagenous structure that is located at the level of the acetabulum. It provides added depth and stability to the joint.

Common conditions of the ligaments and labrum include labral tear, hip dislocation and capsulitis.

Bursa

A burse is a fluid filled sac that decreases friction between two tissues. The primary burse of the hip is the greater trochanter burse. It is located on the outside of the hip between the gluteus mininmus and gluteus medius muscles, into the greater trochanter of the femur. It can become inflamed as a result of direct trauma or overuse.

This condition is referred to as hip bursitis or trochanteric bursitis.

Pelvis

Pelvis, also called bony pelvis or pelvic girdle, in human anatomy, basin-shaped complex of bones that connects the trunk and the legs, supports and balances the trunk, and contains and supports the intestines, the urinary bladder, and the internal sex organs. The pelvis consists of paired hipbones, connected in front at the pubic symphysis and behind by the sacrum; each is made up of three bones—the blade-shaped ilium, above and to either side, which accounts for the width of the hips; the ischium, behind and below, on which the weight falls in sitting; and the pubis, in front. All three unite in early adulthood at a triangular suture in the acetabulum, the cup-shaped socket that forms the hip joint with the head of the femur (thighbone). The ring made by the pelvis functions as the birth canal in females. The pelvis provides attachment for muscles that balance and support the trunk and move the legs, the hips, and the trunk. In the human infant the pelvis is narrow and nonsupportive. As the child begins walking, the pelvis broadens and tilts, the sacrum descends deeper into its articulation with the ilia, and the lumbar curve of the lower back develops.

  • pelvic girdleBones of the pelvic girdle.Encyclopædia Britannica, Inc.
  • Anterior view of the hip and pelvis, showing attachment of ligaments to the femur, ilium, ischium, and pubis.Encyclopædia Britannica, Inc.

Read More on This Topic skeleton: Pelvic girdle The pelvic girdle of the elasmobranch fishes (e.g., sharks, skates, and rays) consists of either a curved cartilaginous structure called…

In the semierect apes, the centre of gravity falls near the shoulder, and the abdominal organs depend from the vertebral column. The ilium is elongated and somewhat spoon-shaped, and the pelvis is oriented horizontally. When a human is standing erect, the centre of gravity falls over the centre of the body, and the weight is transmitted via the pelvis from the vertebral column to the thighbone, the knee, and the foot. Morphological differences from apes include the following: the ilium is broadened backward in a fan shape, developing a deep sciatic notch posteriorly; a strut of bone, the arcuate eminence, has developed on the ilium diagonal from the hip joint (concerned with lateral balance in upright posture); the anterior superior iliac spine, on the upper front edge of the iliac blade, is closer to the hip joint; and the ischium is shorter. The pelvis of Australopithecus africanus—which lived more than two million years ago—is clearly hominin (of human lineage). Homo erectus and all later fossil hominins, including Neanderthals, had fully modern pelvises.

pelvis and leg bones of three great apesComparison of the pelvis and lower limbs of a chimpanzee, an australopith, and a modern human.Encyclopædia Britannica, Inc.

Sex differences in the pelvis are marked and reflect the necessity in the female of providing an adequate birth canal for a large-headed fetus. In comparison with the male pelvis, the female basin is broader and shallower; the birth canal rounded and capacious; the sciatic notch wide and U-shaped; the pubic symphysis short, with the pubic bones forming a broad angle with each other; the sacrum short, broad, and only moderately curved; the coccyx movable; and the acetabula farther apart. Those differences reach their adult proportions only at puberty. Wear patterns on the pubic symphyses may be used to estimate age at death in males and females.

The pelvis is affected by limb-girdle muscular dystrophy, in which voluntary muscles around the pelvic and shoulder areas weaken progressively over time.

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During pregnancy, increasing instability in the pelvic joints can produce a condition known as pelvic girdle pain (PGP). PGP typically resolves on its own in the weeks or months following childbirth, though full recovery may take years.

Functional anatomy of the small pelvic and hip muscles

(completed)

Norwegian version of this page

The deep gluteal muscles or external hip rotators are known contributors to low back, pelvic and hip pain, but our knowledge about their function and accessibility for exercise is insufficient.

Photo: Jan Ringheim, www.kondis.no

To establish an empiric foundation for specific physical actions, we will map the movement range of the deep gluteal muscles in donated human bodies.

About the project

To develop an evidence based understanding of the function of the small and deep pelvic muscles, we will measure changes in muscle length by different rotations of the hip joint. Knowledge on the muscles’ movement range is needed for defining effective physical tests and exercises.

In addition, this knowledge can increase diagnostic understanding of activities that may evoke pain from these muscles, for the benefit for patients groups with low back, pelvic and hip pain.

Objective

Our objective is to develop knowledge about optimal positions for stretching and developing strength from the muscles piriformis, obturator internus and gemellii, quadratus femoris, and obturator externus.

Figure: The deep gluteal (external rotator) muscles on posterior and lateral side of the pelvic and hip area. The superficial muscles gluteus maximus (1) and gluteus medius (2) are excised, to uncover the deep sacrospinosus (3) and sacrotuberalis (4) ligaments and the deep gluteal muscles. (Reproduced from with A. Neumann, Kinesiology of the Musculoskeletal System – Foundations for Rehabilitation, 2nd edition, Chapter 12 Hip, p. 496, Elsevier (2010), with permission).

Background

Pain and disability related to the low back, pelvis, and hip is common. A known alternative diagnosis for joint pain is the piriformis syndrome. Piriformis is a deep gluteal muscle which spans the pelvic and hip joint, and which clinically is associated with several diagnoses and symptoms. Lately another deep pelvic and hip muscle, obturator internus, is proposed as the main obstructer of the sciatic nerve.

The function of the deep pelvic and hip muscles, also called external rotators of the hip, is mainly assessed on human bodies with the hip in a straight position. Only one (unpublished) study on human bodies has empirically assessed the function of these muscles in other positions and found evidence indicating other main functions than external rotation of the hip.

However, exercises for stretching and strengthening of the deep gluteal muscles are still performed with straight hips and with main focus on the external rotator function.

We therefore aim to map out the movement range of the deep pelvic and hip muscles, for establishing an empiric foundation for improved physical actions for patients with low back, pelvic, and hip pain.

Financing

  • The Establishment Foundation for Advancement of Sports Medicine and Sports Physiotherapy in Norway
  • The Norwegian Fund for Post-Graduate Training in Physiotherapy

Collaboration

Knut Rekdahl, Mechanical Workshop, Institute of Basic Medical Sciences, UiO.

Tools

  • Pelvic-hip-specimen will be mounted in a custom made apparatus fixating the pelvic and allowing static positioning of the hip joint in three planes.
  • Muscle lengths will be measured outside the femoral bone by a digital caliper. That is, on non-elastic strings anchored at muscle origins and pulled through muscles and through holes in tendons and bones.
  • Hip positions or joint angles will be decided by an Inertial and Magnetic Measurement System (IMMS, by Xsens). Estimating of the joint angles will be done by an angle dial fixed on the custom-made apparatus and by a hand-held goniometer.

Publications

Vaarbakken K, Steen H, Samuelsen G, Dahl HA, Leergaard TB, Nordsletten L, Stuge B. Lengths of the external hip rotators in mobilized cadavers indicate the quadriceps coxae as a primary abductor and extensor of the flexed hip. Clin Biomech (2014), DOI 10.1016/j.clinbiomech.2014.05.011 (In press)

Start – finish

March 2011 – May 2013

Published Mar. 28, 2012 9:34 AM – Last modified Oct. 26, 2015 10:20 AM

The hip joint is the largest weight-bearing joint in the human body. It is also referred to as a ball and socket joint and is surrounded by muscles, ligaments, and tendons. The thigh bone or femur and the pelvis join to form the hip joint.

Any injury or disease of the hip will adversely affect the joint’s range of motion and ability to bear weight.

The hip joint is made up of the following:

Bones and joints

Ligaments of the joint capsule

Muscles and tendons

Nerves and blood vessels that supply the bones and muscles of the hip

Bones and joints

The hip joint is the junction where the hip joins the leg to the trunk of the body. It is comprised of two bones: the thigh bone or femur and the pelvis which is made up of three bones called ilium, ischium, and pubis. The ball of the hip joint is made by the femoral head while the socket is formed by the acetabulum. The Acetabulum is a deep, circular socket formed on the outer edge of the pelvis by the union of three bones: ilium, ischium and pubis. The lower part of the ilium is attached by the pubis while the ischium is considerably behind the pubis. The stability of the hip is provided by the joint capsule or acetabulum and the muscles and ligaments which surround and support the hip joint.

The head of the femur rotates and glides within the acetabulum. A fibrocartilaginous lining called the labrum is attached to the acetabulum and further increases the depth of the socket.

The femur or thigh bone is one of the longest bones in the human body. The upper part of the thigh bone consists of the femoral head, femoral neck, and greater and lesser trochanters. The head of the femur joins the pelvis (acetabulum) to form the hip joint. Next to the femoral neck, there are two protrusions known as greater and lesser trochanters which serve as sites of muscle attachment.

Articular cartilage is the thin, tough, flexible, and slippery surface lubricated by synovial fluid that covers the weight-bearing bones of the body. It enables smooth movements of the bones and reduces friction.

Ligaments

Ligaments are fibrous structures that connect bones to other bones. The hip joint is encircled with ligaments to provide stability to the hip by forming a dense and fibrous structure around the joint capsule. The ligaments adjoining the hip joint include:

Iliofemoral ligament – This is a Y-shaped ligament that connects the pelvis to the femoral head at the front of the joint. It helps in limiting over-extension of the hip.

Pubofemoral ligament – This is a triangular shaped ligament that extends between the upper portion of the pubis and the iliofemoral ligament. It attaches the pubis to the femoral head.

Ischiofemoral ligament – This is a group of strong fibers that arise from the ischium behind the acetabulum and merge with the fibers of the joint capsule.

Ligamentum teres – This is a small ligament that extends from the tip of the femoral head to the acetabulum. Although it has no role in hip movement, it does have a small artery within that supplies blood to a part of the femoral head.

Acetabular labrum – The labrum is a fibrous cartilage ring which lines the acetabular socket. It deepens the cavity increasing the stability and strength of the hip joint.

Muscles and Tendons.

A long tendon called the iliotibial band runs along the femur from the hip to the knee and serves as an attachment site for several hip muscles including the following:

Gluteals – These are the muscles that form the buttocks. There are three muscles (gluteus minimus, gluteus maximus, and gluteus medius) that attach to the back of the pelvis and insert into the greater trochanter of the femur.

Adductors – These muscles are located in the thigh which help in adduction, the action of pulling the leg back towards the midline.

Iliopsoas: This muscle is located in front of the hip joint and provides flexion. It is a deep muscle that originates from the lower back and pelvis, and extends up to the inside surface of the upper part of the femur.

Rectus femoris – This is the largest band of muscles located in front of the thigh. They also are hip flexors.

Hamstring muscles- These begin at the bottom of the pelvis and run down the back of the thigh. Because they cross the back of the hip joint, they help in extension of the hip by pulling it backwards.

Nerves and arteries.

Nerves of the hip transfer signals from the brain to the muscles to aid in hip movement. They also carry the sensory signals such as touch, pain, and temperature back to the brain.

The main nerves in the hip region include the femoral nerve in the front of the femur and the sciatic nerve at the back. The hip is also supplied by a smaller nerve known as the obturator nerve.

In addition to these nerves, there are blood vessels that supply blood to the lower limbs. The femoral artery, one of the largest arteries in the body, arises deep in the pelvis and can be felt in front of the upper thigh.

Hip movements.

All of the anatomical parts of the hip work together to enable various movements. Hip movements include flexion, extension, abduction, adduction, circumduction, and hip rotation.

The hip joint is a complex structure that provides weight bearing and stability to the human body allowing a greater range of mobility to perform the activities of daily living. The strong muscles and ligaments that support the hip joint enable us to perform actions like running and jumping.

Less …

Hip and thigh

Take a look at these 3 different views of the hip and thigh, showing the superficial muscles.

Side view of hip and thigh

The side view of your hip and thigh shows:

  • the iliac crest (top of the hip bone);
  • gluteus maximus muscle – this muscle makes up most of the flesh of the buttock; its action extends the hip, bringing the thigh into a straight line with the pelvis;
  • iliotibial band (ITB) – a band of strong fibrous tissue that runs down the outside of the thigh;
  • tensor fasciae latae muscle – this contributes to hip flexion and rotation;
  • vastus lateralis, and parts of the rectus femoris and biceps femoris muscles (see below); and
  • the patella (kneecap).

Front view of hip and thigh

From the front (anterior view), you can see the following.

  • The anterior superior iliac spine (bony projection at the front of the hip bone).
  • Most of the quadriceps muscles (rectus femoris and 2 of the 3 vastus muscles – vastus lateralis and vastus medialis) – together with the vastus intermedius muscle (not shown). These muscles create the flesh of the front of the thigh; they act together to extend the knee (e.g. to kick a football).
  • Some of the hip flexor muscles (psoas major, iliacus and iliopsoas).
  • Some of the adductor group of muscles (gracilis, pectineus and adductor longus) – this group adducts, or brings, the thighs together.
  • Sartorius – this has only a weak action on the hip and is more involved in knee movement. It is the most superficial (closest to surface) thigh muscle, so can often be seen and felt.

Back view of hip and thigh

The back (posterior) view of the hip and thigh shows:

  • the 3 hamstring muscles (biceps femoris, semimembranosus and semitendinosus) – these muscles form most of the flesh of the back of the thigh; they flex the knee and extend the hip;
  • gluteus maximus muscle (buttock); and
  • gracilis, sartorius and plantaris muscles.

Information

There are three layers of gluteal muscles on the posterior hips, just like there are three layers of muscles in the abdominal trunk. The largest of them is the most superficial muscle, the gluteus maximus. Its origin is on the ilium of the coxal bone, and it inserts part-way down the shaft of the femur. It helps maintain erect posture, abducts the thigh, and rotates the thigh outward.

Below the gluteus maximus is the smaller gluteus medius. The gluteus medius muscle helps abducts the thigh along with the gluteus maximus, but can rotate the thigh inward where the gluteus maximus rotates the thigh outward.

The below the gluteus medius are several muscles, one of which is the gluteus minimus, the smallest of the gluteal muscles. It is a synergist for the gluteus medius.

Figure 9-7. The three layers of gluteal muscles, gluteus maximus, gluteus medius, gluteus minimus.

Like the forearm, the upper leg, or thigh, has a dense arrangement of many muscles. On the anterior side, the most prominent of the muscles are the sartorius muscle and the four muscles that make up quadriceps muscle group (the “quads”.)

The quadriceps sounds like it should be just one muscle, akin to the triceps brachii, but it is a group of four muscles, three visible on the surface, and the fourth obscured. The three surface muscles of the quadriceps are the rectus femoris in the center, the vastus medialis on the medial side, and the vastus lateralis on the lateral side. These three muscles are visible in Figure 9-8. Below the rectus femoris and largely hidden by it is the vastus intermedius. This muscle’s position can be seen in Figure 9-9. The four muscle of the quadriceps all extend the lower leg, and the rectus femoris additionally can flex the thigh at the hip.

Figure 9-8. The superficial muscles of the thigh.

Figure 9-9. The quadriceps group of four muscles. The view on the left has the rectus femoris cut away to show the vastus intermedius which is below it.

The sartorius muscle is a distinctively long and thin muscle that crosses the thigh diagonally. It is visible in Figure 9-8. Sartorius comes from the Latin for tailor, and this is sometimes called the tailor’s muscle, although the reasons for the nickname are obscure. It may be because the shape of the muscle is thin and long, like a tailor’s measuring tape; it may be because it is close to the inseam a tailor measures when tailoring pants, or it may be because it helps bring about the cross-legged position that tailors often adopt when working.

In the posterior thigh the bulk of the musculature is made up of three long muscles that are collectively called the hamstrings. The origin of this nickname is obscure, but it may have to do with the practice of butchers of hanging the thighs of butchered animals such as pig (the “hams”) by the tendons of these three muscles. Move from the medial edge to the lateral edge of the posterior thigh, the hamstring muscles are the semimembranous muscle, the semitendinosus muscle, and the biceps femoris muscle. Notice the upper leg has a “biceps” muscle just like the upper arm does. This is why you have to indicate which biceps you are taking about when discussing one or other of these muscles. On the medial edge of the posterior thigh is the gracilis muscle. It is also visible on the medial edge of the thigh from the anterior.

Figure 9-10. The muscles of the posterior thigh.

Figure 9-11. The hamstring group of muscles of the posterior thigh.

Lab 9 Exercises 9.4

  1. Using the full-scale leg model, locate and identify the muscles of the thigh listed in the table below.
  1. Write down the muscles of the thigh in the table below and, for each, give the location of that muscle and what effect contracting that muscle has.
Muscle Location & description Action(s)
Rectus femoris
Vastus intermedius
Vastus medialis
Vastus lateralis
Sartorius
Gracilis
Semimembranosus
Semitendinosus
Biceps femoris

Hip Joint Anatomy

Bones and osteology

Femur

The femur is the longest and heaviest bone in the human body. It consists of a superior or proximal end, a shaft, and an inferior or distal end (see the image below).

Parts of femur.

The superior end of the bone is the articulating side of the femur to the acetabulum. The upper femoral epiphysis closes by 16 years of age.

The trabecular bone configuration in the proximal femur obeys Wolff’s Law, which states that bony structures orient themselves in form and mass so as to best resist extrinsic forces. The principal compressive group, the principal tensile group, the greater trochanteric group, the secondary tensile group, the secondary compressive group, and, finally, Ward’s triangle can be found.

The superior end of the femur consists of a head, a neck, and greater and lesser trochanters. The head of the femur is angled superomedially and slightly anteriorly when articulating with the acetabulum. The head is attached to the femoral body or shaft by the neck of the femur.

The superior border of the neck begins just lateral to the femoral head and ends distally at the greater trochanter. The inferior border of the neck begins lateral to the femoral head and extends to the inferior trochanter. The superior border is shorter and thicker than the inferior border. The anterior surface of the neck is rough in comparison to the smooth femoral head. The neck’s posterior surface has a concave appearance. The head and neck are at an angle of 130º (± 7º) to the shaft. The angle is larger at birth and decreases with age.

The greater trochanter is a bony prominence on the anterolateral surface of the proximal shaft of the femur, distal to the femoral neck. It serves as the insertion site for the gluteus medius and gluteus minimus. The lesser trochanter is a bony prominence on the proximal medial aspect of the femoral shaft, just distal to the femoral neck. It serves as the iliopsoas insertion site.

The intertrochanteric line is a raised area that extends from the greater to the lesser trochanter anteriorly. This connection posteriorly is called the intertrochanteric crest, which contains the calcar femorale, another anatomic location on the femoral neck. The calcar femorale is a vertically oriented plate of dense cancellous bone from the posteromedial portion of the femoral shaft radiating superiorly toward the greater trochanter.

Pelvis

At birth, each pelvic half consists of 3 separate primary bones: the ilium, the ischium, and the pubis (see the images below). These bones are joined by hyaline cartilage.

Parts of pelvis. Pelvis and acetabulum, with muscle attachment sites.

In infants and children, these large parts of the hip bones are incompletely ossified. At puberty, the 3 primary bones are still separated by a Y-shaped triradiate cartilage centered in the acetabulum. The primary bones begin to fuse at 15-17 years. Fusion is complete between 20-25 years of age. The fact that these bones were originally separate is fairly undetectable in adult bones on imaging. Although the parts of the hip bone are fused in adulthood, they are still referred to by their separate origins.

Ilium

The ilium is the largest part of the hip bone and makes up the superior part of the acetabulum. The ala provides an insertion point for the gluteal muscles laterally and the iliacus muscle medially.

Anteriorly, the ilium has an anterior superior iliac spine (ASIS); inferior to this is an anterior inferior iliac spine. From the ASIS, anteriorly, the iliac crest comes around laterally and continues posterior to the posterior superior iliac spine (PSIS). The PSIS marks the superior point of the greater sciatic notch.

The lateral surface of the ilium has 3 rough curved lines: the posterior, anterior, and inferior gluteal lines. Medially, the ilium has an iliac fossa. Posteriorly, the medial aspect of the ilium has an auricular surface.

Ischium

The ischium is the inferior aspect of the pelvis. The superior part of the body of the ischium fuses with the pubis and ilium, forming the posteroinferior aspect of the acetabulum.

The ramus of the ischium joins the inferior ramus of the pubis to form a bar of bone called the ischiopubic ramus, which constitutes the inferomedial boundary of the obturator foramen. The posterior border of the ischium forms the lower margin of a deep indentation the greater sciatic notch. The large triangular ischial spine at the inferior margin of this notch is a sharp demarcation separating the greater sciatic notch from a smaller rounded inferior indentation called the lesser sciatic notch.

The bony projection at the inferior end of the body of the ischium and its ramus is the ischial tuberosity.

Pubis

The pubis makes up the anteromedial part of the hip bone and contributes the anterior part of the acetabulum. The pubis has a flat body and 2 rami: superior and inferior.

Medially, the symphyseal surface of the body of the pubis articulates at the pubic symphysis with the surface of the body of the contralateral pubis. The anterosuperior border of the united bodies and symphysis forms the pubic crest. The pubic tubercles, small projections at the lateral ends of this crest where the inguinal ligaments attach medially, are extremely important landmarks of the inguinal regions. The posterosuperior aspect of the superior ramus of the pubis is called the pectin pubis.

The obturator foramen is an oval opening formed by the rami of the pubis and the ischium. The obturator canal houses the obturator nerve and vessels.

Acetabulum

As indicated above, the acetabulum is formed from parts of the ilium, ischium, and pubis. The acetabulum is the cup-shaped socket on the lateral aspect of the pelvis, which articulates with the head of the femur to form the hip joint.

The margin of the acetabulum is deficient inferiorly. An additional fibrocartilaginous margin of the acetabulum is referred to as the acetabular labrum. The labrum functions to deepen the acetabulum, thus holding the femoral head more securely. The lunate is the articular surface of the acetabulum to the femoral head. The rough depression in the floor of the acetabulum is the acetabular fossa, which is continuous with the acetabular notch.

The transverse acetabular ligament is located along the inferior aspect of the acetabulum; it prevents the femoral head from moving inferiorly by deepening the acetabulum inferiorly.

Ligaments

The hip joint contains a strong fibrous capsule that attaches proximally to the acetabulum and transverse acetabular ligament and distally to the neck of the femur anteriorly at the greater trochanter (see the image below). Posteriorly, the fibrous capsule crosses to the neck 1-1.5 cm proximal to the intertrochanteric crest.

Hip ligaments.

Most of the fibers go from the hip bone to the intertrochanteric line, but some deeper fibers go around the neck, forming the orbicular zone, which holds the femoral neck in the acetabulum. The anterior capsule of the hip is the strongest and thickest part.

This capsule is composed of 3 ligaments. The iliofemoral ligament, sometimes referred to as the Y ligament of Bigelow, attaches to the anterior inferior iliac spine and the acetabular rim proximally and takes an inferolateral direction to insert on the intertrochanteric line distally. It is the strongest part of the capsule. The iliofemoral ligament prevents hyperextension of the hip joint during standing by holding the femoral head within the acetabulum.

The ischiofemoral ligament reinforces the capsule posteriorly. It originates on the ischial part of the acetabular rim and spirals superolaterally to the neck of the femur, medial to the greater trochanter. This ligament, like the iliofemoral, also prevents hyperextension and holds the femoral head within the acetabulum.

The pubofemoral ligament reinforces the capsule anteriorly and inferiorly. It begins from the obturator crest of the pubic bone and passes inferolaterally to join the fibrous capsule of the hip joint. This ligament prevents overabduction of the hip joint.

An iliopectineal bursa lies anteriorly over the gap in the ligaments, beneath the iliopsoas tendon.

There are several additional structures of importance related to the fibrous capsule. Lining the fibrous capsule is the synovial membrane. It covers the neck of the femur between the attachment of the fibrous capsule and the edge of the articular cartilage of the head; it also covers the nonarticular area of the acetabulum, providing a covering for the ligament of the femoral head.

Retinacula, which contain blood vessels, are deep longitudinal fibers of the capsule that go superiorly from the femoral neck and blend with the periosteum. The bursa is considered the synovial extension beyond the free margin of the fibrous capsule onto the posterior aspect of the femoral neck.

The ligament of the femoral head is weak. It attaches to the margins of the acetabular notch and the transverse acetabular ligament; its narrow end attaches to the pit in the head of the femur. Usually the ligament contains a small artery to the head of the femur.

A fat pad in the acetabular fossa is covered with synovial membrane. It fills the acetabular area that is not filled by the femoral head.

Nerve supply

The nerve supply to the hip joint is outlined in Table 1 and the images below.

Table 1. Nerves of Hip Joint (Open Table in a new window)

Nerve

Root level

Sensory

Motor

Genitofemoral

L1-2

Proximal anteromedial thigh

None in hip and thigh

Obturator

L2-4

Inferomedial thigh

Gracilis (anterior division)

Adductor longus (anterior division)

Adductor brevis (anterior/posterior division)

Adductor magnus (posterior division)

Lateral femoral cutaneous

L2-3

Lateral thigh

None

Femoral

L2-4

Anteromedial thigh

Psoas major

Sartorius

Articularis genus

Rectus femoris

Vastus lateralis

Vastus intermedius

Vastus medialis

Tibial

L4-S3

None in thigh

Biceps femoris (long head)

Semitendinosus

Semimembranosus

Common fibular (peroneal)

L4-S2

None in thigh

Biceps femoris (short head)

Posterior femoral cutaneous nerve

S1-3

Posterior thigh

None

Hip nerves, lateral view. Hip nerves, anterior view.

Musculature

The muscles of the hip joint are outlined in Table 2 and the images below.

Table 2. Muscles of Hip Joint (Open Table in a new window)

Muscle

Action

Nerve

Sartorius

Hip flexion, external rotation

Femoral nerve

Iliopsoas

Hip flexion

Femoral nerve

Pectineus

Hip flexion

Femoral nerve

Rectus femoris

Hip flexion, leg extension

Femoral nerve

Adductor magnus (anterior part)

Hip flexion, adduction

Obturator

Adductor magnus (posterior part)

Thigh extension

Tibial

Gracilis

Hip flexion, adduction, internal rotation

Obturator

Tensor fascia lata

Hip flexion, abduction

Superior gluteal nerve

Adductor brevis

Hip adduction

Obturator nerve (posterior division)

Adductor longus

Hip adduction

Obturator nerve (anterior division)

Pectineus

Hip adduction, flexion

Femoral

Obturator externus

Thigh external rotation

Obturator nerve posterior division

Gluteus maximus

Lateral rotation, extension

Inferior gluteal nerve

Piriformis

Lateral rotation

Nerve to piriformis

Obturator internus

Lateral rotation

Nerve to obturator internus

Gemellus superior

Lateral rotation

Nerve to obturator internus

Gemellus inferior

Lateral rotation

Nerve to quadratus femoris

Quadratus femoris

Lateral rotation

Nerve to quadratus femoris

Gluteus medius

Hip abduction

Superior gluteal nerve

Gluteus minimus

Hip abduction

Superior gluteal nerve

Semimembranosus

Thigh extension, leg flexion

Tibial

Semitendinosus

Thigh extension, leg flexion

Tibial

Biceps femoris, long head

Thigh extension, leg flexion

Tibial

Biceps femoris, short head

Thigh extension, leg flexion

Common fibular

Hip muscles, lateral view. Hip muscles, anterior view.

Vasculature

The arteries of the hip are outlined in Table 3 and the image below.

Table 3. Arteries of Hip Joint (Open Table in a new window)

Artery

Branches

Obturator

Anterior and posterior branches

Femoral

In femoral triangle, runs in medial thigh between vastus medialis and adductor longus, in adductor canal, through adductor hiatus, then becomes popliteal artery behind knee

Superficial circumflex iliac

Superficial epigastric

Superficial external pudendal

Deep external pudendal

Deep femoral artery

Descending genicular artery

Articular branch

Saphenous branch

Deep femoral artery

Medial circumflex femoral: major supply to femoral neck

Lateral circumflex femoral: also supplies femoral neck

Ascending branch

Transverse branch

Descending branch

Perforators/muscular branches

Artery

Course

Obturator

Artery of ligament teres

Runs through ligament of femoral head

Deep femoral artery

Medial circumflex femoral

Ascending branch

Descending branch

Lateral circumflex femoral

Ascending branch

Cervical branches

Retinacular arteries

Transverse branch

Descending branch

Branches from femoral artery in femoral triangle

Between pectineus and iliopsoas to posterior femoral neck

Runs on quadratus femoris deep to sartorius and rectus femoris to greater trochanter anteriorly

Extracapsular branches of anastomosis

Intracapsular branches: run along neck, enter bone at base of femoral head

Extends laterally

Under rectus femoris

Vascular anatomy of hip.

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