Which muscle plays a key role in controlling the knee?

The popliteus muscle plays a crucial role in controlling the knee, particularly in stabilizing it and assisting with movements such as knee flexion and internal rotation. Located at the back of the knee, the popliteus acts as a "key" that unlocks the knee joint from its full extension during the initial stages of flexion. This action is particularly important during activities that require a transition from standing to bending the knee, such as walking or squatting.

While the quadriceps and hamstrings are prominent muscles involved in knee extension and flexion, respectively, and the tibialis anterior is vital for ankle dorsiflexion, it is the popliteus that specifically contributes to the nuanced control and stabilization of the knee during movement.