Journal of anatomy
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Dissection of 30 human vastus medialis muscles and their nerves has revealed a consistent bipartite nerve supply from the posterior division of the femoral nerve. One part, a short and slender nerve termed the lateral branch, supplies the upper lateral portion of the muscle. The other part, a medial branch, supplies the middle and lower portion of the muscle. ⋯ The lateral branch, which in some cases arises from the nerve that supplies the vastus intermedius, receives a similar spinal input to that of the vastus intermedius. Therefore, whereas the upper portion of the human vastus medialis muscle is closely aligned with the vastus intermedius, the lower third of the muscle has a richer innervation and also shows a distinct gross morphology that, among primates, may be unique to humans. The gross structure of the muscle, taken together with this evidence from the pattern of innervation, suggests that the human vastus medialis is functionally tripartite.