popliteus

The popliteus is a small, thin muscle located in the posterior aspect of the knee, forming part of the deep layer of the posterolateral region of the joint. It lies in the popliteal fossa, where it runs from the lateral femoral condyle to the posterior surface of the tibia, just above the soleal line. The muscle may have a short tendon that blends with the lateral meniscus and the joint capsule.

Origin and insertion: The muscle originates from the lateral aspect of the lateral femoral condyle within the knee joint capsule and inserts on the posterior surface of the tibia above the soleal line. Its tendon typically lies deep to the lateral collateral ligament and superiorly to the proximal tibia.

Innervation and vascular supply: The popliteus is innervated by the tibial nerve, a branch of the sciatic nerve. Blood supply comes from branches of the popliteal artery, including the genicular arteries.

Function: The primary role of the popliteus is to unlock the knee by rotating the femur laterally on the tibia (and, equivalently, aiding tibial rotation during knee flexion). It also acts as a weak accessory knee flexor and helps stabilize the posterior knee during movement and weight bearing.

Clinical significance: Injury to the popliteus or its tendon, or injuries to the posterolateral corner of the knee, can produce posterolateral knee pain and instability, particularly with rotation and flexion. Popliteus pathology is less common than other knee injuries but is recognized in athletes and in cases of knee trauma.

Additional notes: The muscle often serves as a key landmark in surgical approaches to the knee and in imaging assessments of posterior knee structures.