The popliteus does what action?

The popliteus does what action?

• A. Weakly flexes knee
• B. Medially rotates tibia while non-weight bearing
• C. Unloads knee by laterally rotating femur 5 degrees on tibia
• D. Extends knee

Answer: (C)

The action vibrating in the knee’s mechanics is that the popliteus serves as the unlocker of the knee. In a knee that is in the extended, weight-bearing position, the joint is held in a “locked” state by the screw-home mechanism, which involves a medial rotation of the femur on the tibia to maintain extension. The popliteus contracts to reverse that, rotating the femur laterally on the tibia by about 5 degrees. This lateral rotation of the femur on the tibia “unloads” or unlocks the knee, allowing flexion to begin. This is the functional description most aligned with how the muscle is tested: it mainly acts to unlock the knee from full extension by laterally rotating the femur on the tibia. Remember that in a non-weight-bearing (open-chain) context, the popliteus can help initiate flexion by medially rotating the tibia on the femur, but the primary unlocking action in the typical weight-bearing knee is the lateral rotation of the femur on the tibia. It’s not a primary knee extender, and its role as a knee flexor is secondary.

The action vibrating in the knee’s mechanics is that the popliteus serves as the unlocker of the knee. In a knee that is in the extended, weight-bearing position, the joint is held in a “locked” state by the screw-home mechanism, which involves a medial rotation of the femur on the tibia to maintain extension. The popliteus contracts to reverse that, rotating the femur laterally on the tibia by about 5 degrees. This lateral rotation of the femur on the tibia “unloads” or unlocks the knee, allowing flexion to begin.

This is the functional description most aligned with how the muscle is tested: it mainly acts to unlock the knee from full extension by laterally rotating the femur on the tibia. Remember that in a non-weight-bearing (open-chain) context, the popliteus can help initiate flexion by medially rotating the tibia on the femur, but the primary unlocking action in the typical weight-bearing knee is the lateral rotation of the femur on the tibia. It’s not a primary knee extender, and its role as a knee flexor is secondary.