When the anterior cruciate ligament (ACL) in the knee is torn or injured, surgery may be needed to repair it. There are many different ways to do this operation. One is to take a piece of the hamstring tendon from behind the knee and use it in place of the torn ligament. The spot where the tendon is taken is called the “donor site.”
Some researchers say this is a good idea with no problems. Others are sure the hamstring muscle loses strength when the tendon is used as a donor site. The main function of the hamstrings is to bend the knee (knee flexion). If this treatment method affects the muscle function, there should be a change in knee flexion.
Scientists in Japan are studying this problem in adult recreational athletes. They used a CT (computed tomography) scanner to measure the size of the tendon after a piece was removed. They found that there is enough muscle wasting to affect muscle strength. However, overall strength is not lost because the rest of the hamstring muscle takes over for the weakened area. Even the portion of muscle where the tendon was removed works harder to make up for the loss.
A large amount of muscle wasting does occur in a small number of people who have this kind of ACL repair. It only affects athletes involved in sports that require deep knee flexion. This may include judo, wrestling, and gymnastics. These athletes may want to choose a different method of repair for ACL tears. This could include use of the tendon below the kneecap (patellar tendon) or an allograft, replacement material stored in a tissue bank. Leaving the hamstring tendon untouched may help maximize performance after surgery for athletes in these types of sports.