Here's something running backs, wide receivers, rugby players, and ballet dancers have in common: hamstring strains. In fact, acute hamstring strains may be the second most common injury among this group. Only knee injuries top hamstring-related injuries for taking a player or dancer out of commission.

Given the high rate of hamstring injuries, there is a great deal of interest among sports physiotherapists in helping these athletes rehabilitate and return to their sport or performance. In order to do that, an accurate diagnosis is important. But identifying risk factors and predictive factors for injury and reinjury is important.

Studies done so far show that athletes who have injured their hamstring tendon or muscle are twice as likely to reinjure the same tendon/muscle. The older you are and the more you weigh, the higher the risk for a hamstring tear. But weak hamstrings, imbalance in leg muscle strength, and tight hip flexors also increase the risk of a hamstring strain.

What can be done to help these athletes get back to their sports, dance, or other desired athletic activities? The first thing NOT to do is stretch the acutely injured tissue. With the hamstrings (a muscle all athletes spend time stretching), stretching after an acute injury only lengthens the time it takes to get back into action.

Stretching does not seem to lengthen muscle fibers during the healing process. Scar tissue forms as part of the natural healing process. And that scar tissue links up with muscle fibers causing stiffness in the tendon-muscle unit. Researchers are still looking for better ways to lengthen injured/healing hamstring tissue.

In the meantime, studies show it makes much more sense to focus on core training, which will increase trunk stabilization and greatly reduce the risk of reinjury. Agility training is another valuable approach in preventing hamstring reinjury. Eccentric training (starting with the muscle contracted and in a shortened position and moving into positions of elongating the tissue) has some benefit but remains under investigation.

The approach to treatment of acute hamstring tendon/muscle injuries depends on the type and extent of injury. A strain or sprain is different from a full or even partial rupture. Sometimes the tendon pulls away from the bone where it attaches, taking a piece of the bone with it. These are called avulsion injuries and may require surgery.

In order to make a decision about the best treatment approach, an orthopedic surgeon performs various clinical tests and orders imaging studies. X-rays, ultrasound, and MRIs often offer the best diagnostic information with hamstring injuries.

Bleeding into and around the muscle is common with avulsion injuries. Pressure on the sciatic nerve from blood in the area can cause a tingling sensation along the back of the thigh. Surgery may be needed to repair the torn tissue and remove the pressure from the nerve. Hamstring tendons that have retracted pulled away from the bone by more than 2.5 to 3.0 cm (1/4 to 1/2 inch) are especially likely to need surgical repair.

Other less severe strains or hamstring tendinopathymay respond to conservative (nonoperative) care. Tendinopathy refers to a chronic injury with reactive edema (swelling), thickening of the tissue, and scarring but no active inflammation. Care is usually provided by a physiotherapist who will focus on posture, alignment, core strengthening, and soft tissue mobilization. When appropriate hamstring stretching and strengthening may be included in the program.

Safe return-to-sports, dance, or other athletic activities may take some time. Reinjury is always a concern. With acute injuries, the ability to walk without pain is actually very predictive of return to activity. Athletes who can walk pain free within 24-hours of the injury are four times more likely to return-to-sport/activity quickly.

One test that has proven reliable in predicting safe return to activity is called the active hamstring flexibility test. The athlete lies on his or her back with one leg in a knee extension splint. The splinted leg is quickly lifted up off the table as far as it will go. The test is done on both legs. The amount of hip flexion is measured and compared from side-to-side. Equal movement without pain or apprehension in the presence of normal hamstring strength is a good sign the athlete is ready to return to the field or stage.

Reference: Marc Sherry, PT, DPT, LAT, CSCS. Evaluation and Treatment of Acute Hamstring Strains and Related Injuries. In Sports Health. March/April 2012. Vol. 4. No. 2. Pp. 107-114.