osteoarthritis is a type of arthritis that is caused by the breakdown and eventual loss of the cartilage of one or more joints. cartilage is a protein substance that serves as a "cushion" between the bones of the joints. osteoarthritis is also known as degenerative arthritis. among the over 100 different types of arthritis conditions osteoarthritis is the most common affecting over 20 million people in the united states. osteoarthritis occurs more frequently as we age. before age 45 osteoarthritis occurs more frequently in males. after 55 years of age it occurs more frequently in females. in the united states all races appear equally affected. a higher incidence of osteoarthritis exists in the japanese population while south-african blacks east indians and southern chinese have lower rates. osteoarthritis commonly affects the hands feet spine and large weight-bearing joints such as the hips and knees. most cases of osteoarthritis have no known cause and are referred to as primary osteoarthritis. when the cause of the osteoarthritis is known the condition is referred to as secondary osteoarthritis. osteoarthritis is sometimes abbreviated oa.
what is osteoarthritis?