The knee is the largest joint in the human body. I call it a “dumb” joint, because it does what the joints above and below it (hips and ankles) tell it to do. Injury and pain can be due to bio-mechanical problems, ruptured ligaments (ACL or MCL), torn cartilage, and irritation/inflammation of the knee joint caused by overuse, arthritis, osteoporosis, and gout.
Up to 70% of ACL and MCL tears are non-contact. In other words, 7 out of 10 people get serious knee injuries, because of their own bodies, not because pressure was placed on them by outside forces.
Research has shown that rehab is the most effective way to heal a knee injury and eliminate chronic pain. Not only do you have to deal with the pain in the knees, you also have to deal with the hips and calves/ankles, if you want to properly heal the knees and eliminate pain.
A high quality rehab program eliminates knee swelling and pain quickly, then dramatically improves strength, stability and healthy range of motion, which significantly reduces the risk of re-injury. (American J. of Physiology, Journal of Medicine & Science in Sports, J. of Athletic Training, etc.)