vastus medialis, one of the four muscles of the quadriceps femoris group, situated in the medial part of the thigh. It originates from the intertrochanteric line of the femur, the linea aspera, the medial supracondylar line, the tendons of the adductor longus and the adductor magnus, and the medial intermuscular septum. The vastus medialis extends to the lower anterior aspect of the thigh and inserts by an aponeurosis under the patella as part of the quadriceps femoris tendon and onto the medial condyle of the femur. An expansion of the aponeurosis passes to the capsule of the knee joint. The muscle functions in combination with other parts of the quadriceps femoris to extend the leg. Also called vastus internus. Compare rectus femoris, vastus intermedius, vastus lateralis. See also quadriceps femoris.
