Anatomy II: Hip Joint & Popliteal Fossa

• The lecture covers the hip joint and popliteal fossa in Anatomy II (FM 108).
• The students will be able to identify the structures, boundaries, and contents of the popliteal fossa and hip joint.

Popliteal Fossa

• The popliteal fossa is a diamond-shaped intermuscular space located at the back of the knee.
• The fossa is most prominent when the knee joint is flexed.
• The popliteal fossa contains popliteal vessels, the small saphenous vein, common peroneal and tibial nerves, the posterior cutaneous nerve of the thigh, a genicular branch of the obturator nerve, connective tissue, and lymph nodes.

Popliteal Fossa Boundaries

• Laterally, the borders are the biceps femoris muscle superiorly and the lateral head of the gastrocnemius and plantaris muscles inferiorly.
• Medially, the borders are the semimembranosus and semitendinosus muscles superiorly and the medial head of the gastrocnemius muscle inferiorly.
• The anterior wall or floor of the fossa is formed by the popliteal surface of the femur, the posterior ligament of the knee joint, and the popliteus muscle.
• The roof of the fossa is formed by skin, superficial fascia, and the deep fascia of the thigh.

Tibial Nerve

• The tibial nerve is the larger terminal branch of the sciatic nerve.
• It arises in the lower third of the back of the thigh.
• It runs downward through the popliteal fossa, initially lateral to the popliteal artery, then posterior, and finally medial to it.
• The popliteal vein is located between the nerve and artery along the nerve course.
• The nerve enters the posterior compartment of the leg passing beneath the soleus muscle.
• The nerve has cutaneous, muscular, and articular branches.
• The sural nerve descends between the two heads of the gastrocnemius, joining the sural communicating branch of the common peroneal nerve, and supplies the skin of the calf and back of the leg.
• Numerous small branches arise from the sural nerve supply the skin of the calf and the back of the leg.
• The sural nerve accompanies the small saphenous vein, runs behind the lateral malleolus, and supplies skin along the lateral border of the foot and lateral side of the little toe.
• Muscular branches supply both heads of the gastrocnemius, plantaris, soleus, and popliteus muscles.
• Articular branches supply the knee joint, including superior medial, inferior medial, and middle genicular branches.

Common Peroneal (Fibular) Nerve

• This nerve is the smaller terminal branch of the sciatic nerve
• It arises in the lower third of the back of the thigh.
• It runs down through the popliteal fossa along the medial border of the biceps muscle.
• The nerve leaves the fossa by crossing superficially the lateral head of the gastrocnemius muscle.
• It passes behind the head of the fibula, winds laterally around the neck of the bone, pierces the peroneus longus muscle, and divides into the superficial and deep peroneal nerves.
• It is subcutaneous and easily rolled against the bone on the lateral aspect of the neck of the fibula.
• Cutaneous branches include the sural communicating branch joining the sural nerve and the lateral cutaneous nerve of the calf, to supply the skin on the lateral side of the back of the leg.
• The muscular branch goes to the short head of the biceps femoris muscle, which arises high in the popliteal fossa.
• Articular branches serve the knee joint which includes superior & inferior lateral and recurrent genicular branches.

Hip Joint Overview

• Key points to consider for any joint includes, the type, articulating bone, capsule, synovial membrane, intra-articular structures, ligaments, movements, muscles producing movements, stability, nerve supply, and blood supply.
• The hip joint is a ball and socket synovial joint.
• It is a multiaxial (polyaxial) ball and socket joint, designed for stability and weight bearing, yet it compromises mobility.

Articulation

• The articular surfaces of this joint include the spherical head of the femur and the lunate surface of the acetabulum of the pelvic bone.
• The surfaces are covered by hyaline cartilage.
• The acetabulum rim is raised slightly by a fibrocartilaginous collar, called the acetabular labrum.
• Inferiorly, the labrum bridges across the acetabular notch as the transverse acetabular ligament, turning it into a foramen.

Femoral Head Ligament

• A flat shape attaches at one end to the fovea on the head of the femur and at the other end to the transverse acetabular ligament.
• The structure carries a small branch of the obturator artery that supplies the head of the femur.

Capsule

• The capsule is a fibrous membrane that encloses the hip joint, and is strong and thick.
• Medially, it is attached to the margin of the acetabulum, the transverse acetabular ligament, and the adjacent margin of the obturator foramen.
• Laterally, it is attached to the intertrochanteric line on the anterior aspect of the femur and to the neck of the femur, 1cm in front of the inter-trochanteric crest on the posterior surface.

Synovial Membrane

• The membrane attaches to the margins of the articular surfaces of the femur and acetabulum.
• It forms a tubular covering around the ligament of the head of the femur.
• The membrane lines the fibrous capsule of the joint.
• From its attachment to the margin of the head of the femur, the synovial membrane covers the neck of the femur before reflecting onto the fibrous capsule.

Ligaments

• Three ligaments reinforce the hip joint's fibrous capsule and help stabilize the hip joint.
• These ligaments are the iliofemoral, pubofemoral, and ischiofemoral ligaments.
• The iliofemoral ligament is anterior to the hip joint, and is triangular-shaped.
• The apex of the iliofemoral ligament attaches to the ilium, and its base attaches along the intertrochanteric line of the femur.
• The pubofemoral ligament is anteroinferior to the hip joint with a triangular shape, and its base is attached medially to the iliopubic eminence and laterally blending with the fibrous capsule and the iliofemoral ligament.
• The ischiofemoral ligament reinforces the posterior aspect of the fibrous capsule.
• It is medially attached to the ischium, just posteroinferior to the acetabulum, and laterally to the greater trochanter deep to the iliofemoral ligament.
• The transverse acetabular ligament is formed by the acetabular labrum and bridges the acetabular notch, converting the notch into a tunnel for blood vessels and nerves.

Intraarticular Structures

• The labrum acetabular (acetabular labrum).
• The Transverse acetabular ligament.
• and the Round ligament of the femur.

Blood Supply

• The obturator artery
• The medial and lateral circumflex femoral arteries
• The superior and inferior gluteal arteries
• and the first perforating branch of the deep artery of the thigh.

Nerve Supply

• The femoral nerve.
• The obturator nerve.
• The sciatic nerve.
• The superior gluteal nerves.
• And the nerve to the quadratus femoris.

Stability

• The hip joint's strength hinges largely on the shapes of the bones involved in its articulation.
• Strong ligaments also contribute to the stability.

Movements

• Flexion is by the iliopsoas, rectus femoris, and sartorius.
• Extension is by the gluteus maximus and hamstring muscles.
• Abduction is by the gluteus medius, minimus, tensor fasciae latae, and piriformis.
• Adduction is by the adductor longus and brevis, and the adductor fibers of the adductor magnus, assisted by the pectineus and gracilis.
• Medial rotation is by anterior fibers of the gluteus medius and minimus, and the tensor fasciae latae.
• Lateral rotations is by the piriformis, obturator internus and externus, superior and inferior gemelli, and quadratus femoris, assisted by the gluteus maximus.
• Circumduction is a combination of these movements.