Which muscles help resist valgus forces on the knee during single limb stance?

The muscles that help resist valgus forces on the knee during single limb stance are the vastus medialis and semitendinosus.

The vastus medialis plays a crucial role in stabilizing the knee joint by helping to maintain proper alignment, particularly in preventing excessive lateral movement, which is what occurs during a valgus stress. Its strength and activation are vital for countering the forces that tend to push the knee inward (toward a more valgus position).

The semitendinosus, part of the hamstring group, also contributes to knee stability. It acts not only as a knee flexor but also assists in controlling the position of the tibia relative to the femur, thereby providing support against valgus stress.

Together, these muscles work synergistically to ensure that the knee remains stable during single limb stance, which is essential for maintaining overall balance and preventing injury.