The quadriceps.

The quadriceps femoris is a group of muscles located in the front of the thigh. The Latin translation or meaning of "quadriceps" is "four headed," as the group contains four separate muscles: the vastus lateralis, vastus medialis, vastus intermedius, and the rectus femoris. Each of the vastus muscles originates on the femur bone and attaches to the patella, or kneecap. The three vastus muscles are also partially covered by the rectus femoris, which also attaches to the kneecap. However, unlike the vastus muscles, the rectus femoris inserts into the hip bone.

The lateral femoral circumflex artery and its branches supply the quardriceps with oxygenated blood, and the femoral nerve (and its subsequent branches) innervates the muscle group. The quadriceps assist in extending the knee. Since these muscles are used often for walking, running and other physical activities, the quadriceps are prone to injuries including strains, tears and ruptures.