There are different kinds of arthritis. Osteoarthritis is the most common type and is a disease of cartilage, which becomes thinner and thinner as the disease progresses. Its greatest impact is on weight bearing joints such as hips, knees and ankles.
Rheumatoid arthritis is the second most common type, and is a chronic disease. Its cause is unknown. It symptoms include inflammation in joints, muscles, tendons and connective tissues.