Most hamstring injuries occur in the musculotendinous complex. This is the area where the muscles and tendons join. (Tendons are bands of tissue that connect muscles to bones.) The hamstring has a large musculotendinous complex, which partly explains why hamstring injuries are so common.
When the 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 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 muscles cannot begin to heal.
The chemicals that are produced and the blood clotting are your 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.
If the force of the injury is severe enough, the muscle and tendons can tear away from the bone. This happens most often where the hamstring tendons attach to the ischial tuberosity (what you call your “sit bones”). These tears, called avulsions, sometimes require surgery. An incision is made over the back of the thigh where the hamstring muscle is torn. The muscle repair involves reattaching the two torn ends and sewing them together.
If surgery is delayed after an avulsion, the tendon may begin to retract further down the leg, and scar tissue may form around the torn end of the tendon. Both of these factors make it more difficult to do the surgery. With or without surgery, the recovery time can be quite long.
As your hamstrings begin to heal, it is critical that you follow an exercise program to regain your strength and mobility. Specially designed exercises encourage your body to rebuild muscle instead of scar tissue. The exercises also help prevent reinjury. Rehabilitation can be slow, so you will need to be patient and not push yourself too hard or too fast. Returning to active sports like skiing (with the potential for reinjury) must be done only with your surgeon’s approval and after proper rehabilitation.