When the knee is in full extension, the femur slightly medially rotates on the tibia to lock the knee joint in place. Popliteus is often referred to as the "Key" to unlocking the knee since it begins knee flexion by laterally rotating the femur on the tibia. Popliteus is also attached to the lateral meniscus in the knee and draws it posteriorly during knee flexion to prevent crushing the meniscus between the tibia and femur as the knee flexes. Additional images See also Posterolateral knee Surgery Injury to the Popliteus causes posterolateral rotatory instability of knee. This can be treated with Arthroscopic Popliteus Sling reconstruction using the popliteus portal. References External links PTCentral Calf muscles Muscles of the lower limb