Recently a much greater understanding has developed about the causes of knee dysfunction. Knowledge has been available for a long time about torn knee cartilages and ligaments, arthritis, and loose bodies in the knee. Newer knowledge explains why many of these conditions develop - even torn cartilage and ligaments. Certainly a ligament or cartilage tear can be a direct, primary development, caused by a person being tackled in football or from some other direct injury. Often these injuries develop when a football player is running and suddenly cuts, or when a person is simply getting up from a stooped position. In other words, the problem develops during an activity similar to that done on a day-to-day basis without injury. Suddenly, for some reason, an injury develops from the same activity.

The knee is generally considered a simple hinge-type joint which is moved through its range of motion by the muscles attached to it, primarily giving movement to straighten or bend the leg. The joint contains two pads, called the similunar cartilages. Sometimes the cartilage can be torn and require surgery. Surgery may also be necessary to remove loose bodies from inside the joint, and to tie torn ligaments back together.

The muscle were once considered simply the motors that move the bones of this joint. However, it has been recognised in applied kinesiology that the muscles also provide stabilisation to the joint, along with the ligaments which limit the joint's range of motion. Many knee problems are the direct result of improper support to the knee joint from the muscles which attach above and below it.

If one or a group of these muscles becomes weak, the knee loses its stability in that direction. For example, if the muscle(s) on the middle side of the knee is weak, there is little to keep the knee from bending toward the center. If this condition is present and an individual strains his knee in that direction, there ins't much to keep the knee from jamming. This can cause something as simple as a trick knee or a much more serious condition, such as a catching of the cartilage as the knee goes through its range of motion, causing a tear to occur.

By testing the individual muscles which support the knee, an applied kinesiologist can find the area of limited strength. Further evaluation of the weakened muscle gives the doctor information to effect its strengthening. Usually, the cause of the problem is rapidly found and removed, providing an immediate strengthening of the muscle(s) at fault.