vastus

Vastus is a term used in human anatomy to refer to three broad muscles that comprise the vastus portion of the quadriceps femoris in the front of the thigh: vastus lateralis, vastus medialis, and vastus intermedius. The name comes from Latin and reflects their wide, flat shape and location on the anterior thigh.

Anatomy and connections: The three vasti arise from the femur. Vastus lateralis originates from the greater trochanter and the lateral lip of the linea aspera; vastus medialis from the intertrochanteric line and the medial lip of the linea aspera; vastus intermedius from the anterior and lateral surfaces of the femoral shaft. All three insert into the quadriceps tendon, which encircles the patella and continues as the patellar ligament to the tibial tuberosity. The vasti are innervated predominantly by branches of the femoral nerve and receive blood supply from branches of the femoral artery, with contributions from perforating arteries of the profunda femoris.

Function: The primary role of the vastus muscles is to extend the knee joint. They work together with the rectus femoris and other quadriceps components to straighten the leg, stabilize the knee, and contribute to activities such as standing, walking, running, and jumping. The vastus medialis, particularly its oblique portion in some descriptions (vastus medialis obliquus), is noted for aiding patellar tracking and medial stabilization of the patella.

Clinical relevance: Weakness or imbalance among the vasti can contribute to knee pain, patellofemoral disorders, or reduced knee extension strength. Injury or atrophy after knee trauma or surgery is commonly addressed with targeted quadriceps strengthening and rehabilitation.