Final answer:
Medial internal rotation of the femur is a movement at the hip that brings the thigh closer to the midline and assists in stabilizing the knee when extended by locking it into place.
Step-by-step explanation:
Medial internal rotation of the femur is a movement at the hip joint that brings the anterior surface of the thigh closer to the body's midline. This action is opposed by lateral rotation, where the anterior surface moves away from the midline. At the knee, medial rotation of the femur also plays a role during extension; as the knee reaches full extension, the femur slightly rotates medially to "lock" the knee into a stable position.
Furthermore, the medial meniscus is a C-shaped fibrocartilage found in the knee, which provides a cushion between the medial femoral condyle and the tibia, supporting the weight-bearing function of the knee during these movements. The muscles that help in medial rotation at the hip include the anterior fibers of the gluteus medius and minimus, among others.