Tears in the anterior cruciate ligament (ACL) of the knee are common sports injuries. Athletes with torn ACLs may end up wearing a brace to help support the injured knee. Research has shown that knee braces can help prevent too much movement in knees with a torn ACL. Braces seem to help in situations when weight is borne on the foot (weightbearing) and also when it’s not (nonweightbearing). Still, even braced knees are often injured again.
These researchers studied what happens during the transition between nonweightbearing and weightbearing–for example, landing after a jump. They used a special machine to measure the movement of the knee joint in nine people with ACL tears. The results were compared for each person’s healthy knee and injured knee.
The results showed that bracing definitely helped keep the knee joint from moving too much during weightbearing and nonweightbearing. But in the transition, all the injured knees showed much more movement. This part of the testing showed an average of 3.5 times more laxity (looseness) in the injured knees than the healthy knees.
These results help explain why athletes with braced knees after ACL tears often experience injuries when quickly changing directions or landing from a jump. What researchers would like to know is how much joint movement is too much. That knowledge would help them develop a better knee brace for ACL tears.