The vastus lateralis muscle is located on the side of the thigh. This muscle is the largest of the quadriceps group (often called quads) which also includes the rectus femoris, the vastus intermedius, and the vastus medialis. Collectively, the quadriceps muscle is the largest in the human body and its purpose is to extend the knee. The specific task of the vastus lateralis muscle is to extend the lower leg and allow the body to rise up from a squatting position.
On the upper end, the muscle attaches to the femur; on the lower end it attaches to the patella, or kneecap. Taken together, the muscles of the legs allow strength and stability. They provide power for and absorb the impact of daily activities such as walking, running, and jumping.
Common injuries to the vastus lateralis muscle include strains and contusions. A strain is actually a tear in the muscle and can result from an improper warm up before physical activity. A contusion is when the muscle is crushed against the bone, and is usually the result of an impact such as a bruising injury.