Muscle · Thigh

Vastus intermedius

Musculus vastus intermedius

Vastus intermedius is the quadriceps you never see. It lies flat against the front of the femur underneath rectus femoris, sandwiched between its two neighbours, and it pulls the kneecap straight up the line of the thigh bone. Its deepest slips have a name of their own — articularis genus — and a job worth knowing: they hitch the pouch of joint lining above the kneecap upwards as the knee straightens, so it does not get pinched in the joint. Because it sits directly on bone and cannot be reached by hand, it is the quadriceps that gets forgotten, and after a femoral fracture or a long spell in a brace it is often where the adhesions and the lost extension actually live.