The body adapts well to injury. One example is how the motion of the knee changes after the anterior cruciate ligament (ACL) is torn. Walking patterns during the gait cycle are the subject of this new study. The gait cycle is used to describe movements of the body and limbs beginning when one foot hits the ground and ending when that foot lands again.
Researchers at the University of Athens Medical School in Greece teamed up with scientists University of Nebraska in the United States. They used a three-dimensional (3-D) optoelectric system to film, record, and measure the gait cycle.
There were three groups in the study: people with normal knees, patients with a torn and unrepaired ACL, and patients with a torn ACL that had been repaired. The researchers studied bending and straightening, side-to-side motion, and rotation.
Only one movement was affected by damage to the unrepaired ACL. It was rotation of the lower leg bone (tibia) during walking. The tibia in the knees with an unrepaired ACL rotated inward when the leg swung forward. Normal knees without ACL damage and knees with repaired ligaments rotated outward.
The authors of this study don’t know if this is a long-term problem. If it is, then even a simple activity such as walking increases the risk of more knee damage. However, there may be other ways the body compensates for the lost ACL. For example, the hamstring muscle behind the knee may contract when the leg is straight. This would protect the knee by keeping the tibia from moving forward and rotating abnormally.
New 3-D technology is making it possible to revisit some issues, such as knee motion in all planes and movements after ACL injury. Changes in walking patterns after the ACL is torn may lead to further damage to the joint and bone. Specialized equipment can now be used to study the effects of exercise programs on knee motion and the gait cycle.