QUADRICEPS GROUP
The quadriceps group consists of four muscles united by a common patellar tendon (arrow). The individuals muscles are the: a. vastus lateralis, b. the rectus femoris, c. the vastus medialis and d. the vastus intermedius (on this leg, the overlying rectus femoris has been removed). These muscles have origins on various portions of the os coxa and femur. They all insert on the tibial tuberosity by way of the patellar tendon. The primary action of this group is extension of the lower leg at the knee.