Posterior Thigh and Popliteal Fossa Anatomy

Posterior Thigh and Popliteal Fossa

• The posterior thigh and popliteal fossa are anatomical areas of the lower limb.
• The femur is the longest, strongest and largest bone in the body.
• Structures of the posterior thigh and popliteal fossa overlay the femur.
• The pelvis is where many of the posterior thigh and popliteal fossa structures originate, specifically the gluteal areas.
• The posterior compartment of the thigh has boundaries including the lateral intermuscular septum and adductor magnus. It also has deep fascia.
• The contents of the posterior compartment of the thigh include the hamstrings, nerves, and vascular structures.
• Common properties of the posterior compartment include shared actions of knee flexion and hip extension (primarily), innervation by the sciatic nerve (mostly the tibial portion), and a shared blood supply from the profunda femoris.
• The hamstrings are the semimembranosus, semitendinosus, and biceps femoris (long and short heads).
• The Semimembranosus: Originates from the superior lateral quadrant of the ischial tuberosity, inserts on the posterior surface of the medial tibial condyle, its actions include knee flexion, hip extension and medial knee rotation. Key antagonists are knee extensors and hip flexors. Innervated by the tibial portion of the sciatic nerve.
• The Semitendinosus: Originates from the medial facet of the ischial tuberosity, inserts on the medial tibial condyle. Actions include knee flexion, hip extension, and medial knee rotation. Key antagonists are knee extensors and hip flexors. Innervated by the tibial portion of the sciatic nerve.
• The Biceps Femoris (long head): Originates from the medial facet of the ischial tuberosity, inserts to the head of fibula, LCL ligament and lateral tibial condyle. Actions include knee flexion, hip extension and lateral knee rotation. Key antagonists are knee extensors and hip flexors. Innervated by the tibial portion of the sciatic nerve.
• The Biceps Femoris (short head): Originates from the linea aspera, lateral supracondylar line, inserts to the head of fibula, LCL ligament and lateral tibial condyle. Actions include knee flexion and lateral knee rotation. Key antagonists are knee extensors. Innervation is by the sciatic nerve (common peroneal portion).
• The pes anserinus is a bursa on the medial side of the knee that looks like a goose foot.
• Tendons insert to the medial side of the knee. Structures include sartorius, gracilis, semitendinosus, and semimembranosus structures.
• The pes anserinus assists in stabilizing the medial knee and pelvis.
• Hip flexion is limited by hamstring flexibility, and should be >70°. Sciatic nerve tension and tight hip ligaments can restrict hip flexion.

Popliteal Fossa

• The popliteal fossa is a diamond-shaped space located behind the knee.
• Boundaries: medial and lateral heads of the gastrocnemius (plantaris), biceps femoris, semimembranosus/semitendinosus.
• Floor: posterior surface of the femur, knee joint capsule, oblique popliteal ligament, and popliteus muscle.
• Ceiling: deep fascia and adipose tissue; part of the posterior femoral cutaneous nerve and small saphenous vein are embedded in adipose tissue.
• Contents: tibial nerve, popliteal artery, popliteal vein, common peroneal nerve, lymph vessels and nodes.
• Significance: pulse palpable and dopplerable; bakers cyst can present, and the area allows injections (e.g., LA).

Nerves

• The sciatic nerve arises from the sacral plexus and includes L4, L5, S1, S2, S3 nerves.
• The sciatic nerve has two distinct portions: tibial and common peroneal.
• The sciatic nerve usually splits mid-thigh. Variations can include more proximal or distal splits.
• All hamstrings are innervated by the tibial portion of the sciatic nerve (except the short head of biceps femoris).

Vascular Supply

• The femur and hamstrings are supplied by the profunda femoris artery.
• The posterior compartment is drained by the profunda femoris vein.
• Lymphatics also aid in drainage.

Summary

• Students should be able to identify and understand the function of the hamstrings.
• They should identify major nerves within the posterior thigh and popliteal fossa, understanding their innervation and cutaneous areas served.
• Students should identify the major vascular structures.
• They should have a basic understanding of the area's clinical significance and the impact of injuries/conditions.