Back

Taking Pains to Avoid Ligament Strains

A torn knee ligament, such as the anterior cruciate ligament (ACL), often requires surgical reconstruction. Exercise is important after the operation to keep the muscles from wasting and weakening. The challenge is to exercise the muscles without straining the healing graft.

In this study, researchers try to find out how much strain four commonly prescribed exercises put on the ACL. The exercises are: (1) the step up, (2) the step down, (3) the lunge, and (4) a one- legged sit to stand. A small probe was put inside the joint and used to measure joint movement. The measurements were converted to tell how much strain is put on the ACL. Each subject did the four exercises while the researchers recorded the position of the knee joint and the strain on the ligament.

The authors report no difference in strain from one exercise to the next. The four exercises used in this study didn't produce any greater strain than the two-legged squat used most often in rehab. The flexion angle of the joint didn't seem to make a difference either. If anything, having the knee straight put more strain on the ACL.

Exercises chosen to rehab a reconstructed ACL should be based on how much strain is placed on the healing graft. The results of this study suggest working with the joint flexed during the early phase of rehab. Working with the joint in a fully extended position may cause damage to the healing graft. Lunges and parallel squats are safe. Step-up, step-down, and mini-squats are usually done with the knee close to full extension and put more strain on the ACL. Physical therapists may want to wait to add these exercises until later in the rehab process.

References: Annette Heijne, et al. Strain on the Anterior Cruciate Ligament During Closed Kinetic Chain Exercises. In Medicine & Science in Sports & Exercise. June 2004. Vol. 36. No. 6. Pp. 935-941.

Back