Anatomy, Bony Pelvis and Lower Limb, Popliteus Muscle

Despite its small size, the popliteus is a major stabilizer of the knee. The popliteus is involved in both the closed chain phase and open chain phase of the gait cycle. During the closed chain phase, which is when the foot is in contact with the ground, the muscle externally rotates the femur on the tibia. In the open chain phase, or swing phase of the limb, the popliteus acts to internally rotate the tibia on the femur. The popliteus is accompanied by the tibialis posterior, flexor digitorum longus, and flexor hallucis longus forming the deep posterior compartment of the leg. It forms the base of the popliteal fossa and is the only muscle of either the deep posterior or superficial posterior fossa to act solely on the knee joint as a posterolateral stabilizer.Often overlooked as a critical stabilizer of the knee joint, the popliteus can commonly be involved in posterolateral corner injuries of the knee. These injuries typically occur secondary to a varus force or direct blow to the knee (from medial to lateral). Diagnostic imaging of choice is magnetic resonance imaging (MRI) for evaluation and dysfunction. MRI can also point to other related issues within the knee. An iatrogenic popliteal injury may result in a future poor functional outcome and is critical to address, particularly following knee reconstruction surgery. Patients with anatomically smaller knees may also be at increased risk for popliteal injury.