Popliteus muscle

Popliteus is a small muscle which is often described as the key of the knee joint. It unlocks the knee joint by rotating the femur at the beginning of knee flexion to allow full knee flexion to occur.

Origin: Lateral condyle of the femur

Insertion: Upper posterior surface of the tibia, above the soleal (popliteal) line

Actions: Knee flexion

Internal rotation of the knee when it is flexed

Innervation: Tibial nerve

Daily uses: Walking