Researchers suspect that osteoarthritis is caused by a combination of factors in the body and the environment. The chance of developing osteoarthritis increases with age. By age 65, half of the population has x-ray evidence of osteoarthritis in at least one joint, most often in the hips, knees, or fingers.
Osteoarthritis often results from years of wear and tear on joints. This wear and tear mostly affects the cartilage, the tissue that cushions the ends of bones within the joint. Osteoarthritis occurs when the cartilage begins to fray, wear away, and decay.
Putting too much stress on a joint that has been previously injured, improper alignment of joints, and excess weight all may lead to the development of osteoarthritis.