Hamstring Injuries

The big group of muscles and tendons in the back of the thigh are commonly called the hamstrings. Injuries in this powerful muscle group are common, especially in athletes. Hamstring injuries happen to all types of athletes, from Olympic sprinters to slow-pitch softball players. Though these injuries can be very painful, they usually heal on their own. But for an injured hamstring to return to full function, it needs special attention and a specially designed rehabilitation program.

A hamstring may be pulled, partially torn, or completely torn. In the rare case of a complete tear, the pain is excruciating. The torn tissues may form a hard bunch in the back of the thigh when the leg is bent. The skin may also bruise, turning purple from bleeding under the skin. This is not necessarily dangerous but can look somewhat alarming.

What are the Hamstrings?

The hamstrings make up the bulk in back of the thigh. They are formed by three muscles and their tendons. The hamstrings connect to the ischial tuberosity, the small bony projection on the bottom of the pelvis, just below the buttocks. There is one ischial tuberosity on the left and one on the right. The hamstring muscles and their tendons are laterally and medially bound to the posterior region of the knee.

The inner hamstring includes the tendons of the gracilis, sartorius, and two other muscles of the leg. The outer hamstring is associated with the tendon of the biceps muscle of the thigh. The hamstring muscles run down the back of the thigh. Their tendons cross the knee joint and connect on each side of the shinbone (tibia). The hamstrings function by pulling the leg backward and by propelling the body forward.

What happens when a hamstring is injured?

Most hamstring injuries occur in the musculotendinous complex. This is the area where the muscles and tendons join. These tendons are bands of tissue that connect the hamstring muscles to the bones of the leg and pelvis. The hamstring has a large musculotendinous complex, which partly explains why hamstring injuries are so common.

When a hamstring is injured, the fibers of the muscles or tendon are actually torn. The body responds to the damage by producing enzymes and other body chemicals at the site of the injury. These chemicals produce the symptoms of swelling and pain.

In a severe hamstring injury, the small blood vessels in the muscle can be torn as well. This results in bleeding into the muscle tissue. Until these small blood vessels can repair themselves, less blood can flow to the area. With this reduced blood flow, the damaged muscles of the hamstring cannot begin to heal.

The chemicals that are produced and the blood clotting are the body's way of healing itself. Your body heals the muscle by rebuilding the muscle tissue and by forming scar tissue. Carefully stretching and exercising your injured muscle helps maximize the building of muscle tissue as you heal.

In rare cases, a hamstring injury can cause the muscle and tendons to tear away from the bone. This happens most often where the hamstring tendons attach to the ischial tuberosity. These tears, called avulsions, sometimes require surgery in order to heal properly.