The knee really depends on the muscles around it for stability. It also depends on the ligaments inside the joint to help hold it together. The surfaces of the two major bones that connect to form the knee are not smooth, perfectly matched surfaces. This is especially true on the outside edge of the knee joint. That’s one main reason the knee needs strong muscles and ligaments. These structures are at risk for injury because large or sudden forces at the knee can disrupt the ligaments. The anterior cruciate ligament (ACL) of the knee is especially prone to injury.
Anything that injures the muscles or ligaments can affect the knee’s ability to sense its position as it moves. This “position sense” is called proprioception. Proprioception can be difficult to measure. One way to measure it is to compare the point in time when the leg begins to move with when that motion is detected by the person. Physical therapists often measure proprioception by moving a patient’s leg into a position and then asking the patient to move his or her other leg into the same position without looking.
Studies have shown that not everyone with knee injuries has this type of damage. People with chronic unrepaired ACL tears have changes in knee proprioception. Some people who have had surgery to repair the ACL also have this type of damage. Researchers think that proprioception is impaired in more cases, but the difficulty of measuring it prevents them from proving it.
One group of researchers looked at the effects of bracing and bandaging on knee proprioception. They chose a group of people with ACL injuries that had been surgically repaired. They also looked at the results of other similar studies. There were a variety of results. Some studies reported no loss of proprioception after injury or surgery. Others showed loss of proprioception and improvement with bandaging the knee.
In their own study, these authors found that bracing did not produce any changes in detecting motion after surgery. Patients were measured after surgery and two years later. Differences in research results may be explained by differences in injury, differences in surgery, and when or how measurements were taken.
Does wearing a brace after ACL injury and/or surgery help improve position sense? More studies are needed to help clear up the confusion on this issue. For now, a brace of some type seems most helpful for patients who continue to have pain and problems and do not choose surgery.