The rectus femoris muscle is one part of the large, fleshy group of leg muscles called the quadriceps femoris. This muscle grouping occupies the front and sides of the thigh and is primary extensor of the knee. It is composed of four parts - rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. These parts connect the ilium and femur to a common patellar tendon, which passes over the front of the knee and attaches to the patella (knee cap). This tendon then continues as the patellar ligament to the tibia (lower leg bone).