The word arthritis can be translated as “joint inflammation ”. It's not very accurate of a term, however, since there really is no actual inflammation, there is, however, a deterioration of the surface of the joint, (also known as the joint cartilage) which results in the bone underneath being exposed, a shrinking of the space of the joint, and a maddening nagging type of pain that can drive the person suffering from it mad.

To be clear, the type of arthritis found in the knee is most often osteoarthritis, not the more common and more crippling rheumatoid arthritis found in the rest of the body. It can be caused in the knee by average wear or by an injury of some kind. Often it's caused by the kneecap not tracking – or moving – properly against the rest of the knee structure. It can begin an entire sequence of inflammation, which leads to softening of the joint surface, then local destruction of the joint surface which leads to chemical substances being released into the joint. The chemicals, however, end up doing more harm than good and start off a harmful chain reaction in the entire joint.

The original cause of the arthritis is almost irrelevant, the wrong treatment or no treatment at all can lead the patient to the same suffering.

When the kneecap isn't moving correctly within the knee itself, part of it presses against the femur in the leg too hard, while the rest of the kneecap presses against it with not enough pressure. The balance of the kneecap is thrown off, and this can cause serious problems since the kneecap is designed to need a balanced pressure to release the nutrients from the fluid from the joint it's sitting in. When the balance is off, the cartilage in the joint can soften and swell then minute blisters and sometimes small fissures can form, which in turn break into things called fibrils. These fibrils can then break away from the knee tissue and get stuck in the fluid around the knee. This process releases bad enzymes throughout the knee and can cause serious problems.

Where the abnormal plica (A plica is a fold of the soft inner lining of the knee joint 'the 'synovium') touches the bone underneath the knee, it can become red and thickened. The underlying surface of the joint can become tender and the exact same cycle of destruction of enzyme release described above that spreads damage to other parts of the knee joint.

When the cohesion of the knees' natural cushion is reduced, the joint can become unstable. A piece of loose cartilage can also move over and immobilize the joint, damaging the front of the knee even further. The joint will then undergo essentially the same destructive course, with the damaging enzyme further infiltrating the knee.

The one positive when it comes to osteoarthritis of the knee is that it is not a sign that you will be more likely to suffer arthritis in your other joints. Most knee arthritis is caused by a physical problem within the knee itself and if identified and repaired early enough, recovery is likely and a lifetime of healthy knees is possible.