Osteoarthritis, also called degenerative joint disease and osteoarthrosis, is the most common form of arthritis. It is characterized by the breakdown of cartilage in joints (i.e., intersections of two bones) and is often caused by “wear and tear.” Cartilage cushions the ends of the bones and allows for easier movement within the joints. As osteoarthritis progresses, bone spurs (osteophytes) develop within the affected joint and the joint space narrows, increasing pain and decreasing mobility.

Osteoarthritis causes joint pain and stiffness and may result in loss of joint function. The disease, which can cause significant disability, is the reason for most knee and hip replacement surgeries.

Symptoms of osteoarthritis (e.g., joint pain and stiffness, loss of joint function) usually develop between the ages of 40 and 60. The condition primarily affects the weight-bearing joints (e.g., knees, hips, feet, back). It also may affect the neck and the joints in the fingers and hands.

There are 2 types of osteoarthritis—primary and secondary. Primary osteoarthritis is associated with aging, and secondary osteoarthritis is associated with an additional cause, such as injury, heredity or obesity.

Incidence and Prevalence of Osteoarthritis

According to the Arthritis Foundation, osteoarthritis is the most common joint disease in the United States, affecting approximately 21 million people. The condition is more common in patients over the age of 45. Prior to age 55, more men are affected than women, but after the age of 55, osteoarthritis is more common in women.