The major types of arthritis that affect the foot and ankle are osteoarthritis, rheumatoid arthritis, and posttraumatic arthritis.

Osteoarthritis Osteoarthritis, also known as degenerative or "wear-and-tear" arthritis, is a common problem for many people after they reach middle age, but it may occur in younger people, too.

In osteoarthritis, the cartilage in the joint gradually wears away. As the cartilage wears away, it becomes frayed and rough, and the protective space between the bones decreases. This can result in bone rubbing on bone, and produce painful osteophytes (bone spurs).

In addition to age, other risk factors for osteoarthritis include obesity and family history of the disease.

Osteoarthritis develops slowly, causing pain and stiffness that worsen over time.

Rheumatoid Arthritis (Top) Osteoarthritis that has progressed to bone rubbing on bone and bone spurs. (Bottom) Swollen, inflamed synovium and joint deformity are signs of rheumatoid arthritis.

Reproduced from The Body Almanac. © American Academy of Orthopaedic Surgeons, 2003. Rheumatoid arthritis is a chronic disease that can affect multiple joints throughout the body, and often starts in the foot and ankle. It is symmetrical, meaning that it usually affects the same joint on both sides of the body.

Rheumatoid arthritis is an autoimmune disease. This means that the immune system attacks its own tissues. In rheumatoid arthritis, immune cells attack the synovium covering the joint, causing it to swell. Over time, the synovium invades and damages the bone and cartilage, as well as ligaments and tendons, and may cause serious joint deformity and disability.

The exact cause of rheumatoid arthritis is not known. Although it is not an inherited disease, researchers believe that some people have genes that make them more susceptible. There is usually a "trigger," such as an infection or environmental factor, which activates the genes. When the body is exposed to this trigger, the immune system begins to produce substances that attack the joints.

Posttraumatic Arthritis Posttraumatic arthritis can develop after an injury to the foot or ankle. Dislocations and fractures—particularly those that damage the joint surface—are the most common injuries that lead to posttraumatic arthritis. Like osteoarthritis, posttraumatic arthritis causes the cartilage between the joints to wear away. It can develop many years after the initial injury.

An injured joint is about seven times more likely than an uninjured joint to become arthritic, even if the injury is properly treated. In fact, following an injury, your body may actually secrete hormones that stimulate the death of your cartilage cells.