The knee joint is a hinged joint comprised of three bones, the femur (thigh bone), tibia (shin bone), and the patella (knee cap). The femur and tibia are held together by two sets of ligaments, the medial and lateral collateral ligaments and the anterior and posterior cruciate ligaments. The patella is held to the front surface of the femur by retinacular ligaments on each side. Articular cartilage covers the ends of the femur and tibia and the back of the patella. This cushiony coating compresses under load to protect the underlying bone. A meniscus cartilage on each side of the knee acts as a shock absorber to also protect the surfaces of the knee joint.
Any of these structures can be damaged from injury or the degenerative effects of aging. Meniscus tears and ligament ruptures are common sports-related injuries which can lead to pain and instability when attempting to resume an activity. Degenerative changes from aging occur in the meniscus cartilages and the articular cartilage which make these structures more prone to tearing and wearing thin. The worn cartilage can eventually wear away completely, exposing the underlying bone and making weight bearing painful. This degenerative process resulting in loss of articular cartilage is known as osteoarthritis.
Although some of the injuries to the cartilage and ligaments are best treated with surgery, there are several conservative measures that should be tried before resorting to an operation. Following an injury, it is important to see a knee specialist who can accurately diagnose the problem and recommend the appropriate treatment. For chronic conditions of the knee, a trial of anti-inflammatory medication, activity modification, weight reduction, and possibly supervised physical therapy may help alleviate or reduce the pain to a manageable level.