What Causes Osteoarthritis?

What causes osteoarthritis?

There are good reasons to believe that neither aging nor the normal use of joints causes osteoarthritis. But exactly what the cause of osteoarthritis is remains unknown. In one study, no obvious cause could be found in more than 90% of people with osteoarthritis.

There are hints that active disease processes are involved that upset the normal breakdown and remodeling of cartilage. Some researchers suggest that inappropriate loads placed on the bones may change the way their metabolism works. This can happen when the bones are used too much or not enough, when injuries occur that upset normal joint function, or when unusual stress is placed on the joint (by, say, operating a jackhammer).

Recent evidence suggests, too, that certain enzymes (metalloproteinases) are involved in the destruction of cartilage and bone in osteoarthritis. And, the loss of glycosaminoglycans (large molecules that help trap water) by cartilage during the disease process also may play a role.

Conditions That Can Cause Osteoarthritis

Although osteoarthritis can occur by itself, it also may arise as a result of other conditions. The disease can be caused by bone disorders or certain inherited diseases. Sometimes, the disease is caused by derangements of metabolism or malfunction of internal glands. Other conditions that can cause osteoarthritis include:

• Injury to Joints. Repeating movements that put stress on a joint can eventually lead to osteoarthritis. Apparently, movements that our joints are not used to will cause problems. Direct impact on joints also may loosen tendons or damage cartilage, which can lead to osteoarthritis.
• Meniscus Injury and Repair of the Knee. Many knee injuries also tear a meniscus. If the meniscus injury is severe enough, it may have to be repaired surgically. Both the injury and its repair increase the chances that osteoarthritis will develop in the affected knee.
• Instability of Weight-Bearing Joints. Small changes in the mechanics of a joint, such as instability or changed shape of the joint, may contribute to the development of osteoarthritis.
• Inflammation of Joints. Rheumatoid arthritis and several other, less common, types of arthritis with accompanying inflammation can lead to osteoarthritis.