Arthritis occurs when the area around a joint becomes swollen and causes pain, stiffness, and limited mobility. Osteoarthritis (a.k.a. degenerative joint disease) is the most common form of arthritis and typically affects the hands and weight-bearing joints such as the hips, knees, and spine. Osteoarthritis occurs when the cartilage that normally covers the ends of bones disintegrates as a result of age or overuse. Without the cartilage acting as a protective barrier, the bones rub together, creating friction. Rheumatoid arthritis is an autoimmune reaction where the body mistakenly begins to attack itself, causing swelling in the joint lining, typically in the hands, wrists, and knees. In severe cases, rheumatoid arthritis can affect the skin, eyes, lungs, and nerves. Some of the risk factors for arthritis include age, gender (arthritis is more prevalent in women than in men), obesity, and work factors such as heavy lifting or repetitive motions. Physical therapy treatment of arthritis focuses on decreasing pain and increasing joint mobility and strength through exercises, stretches, hot and cold therapy, and pain management techniques. Some forms of arthritis can be prevented by maintaining a healthy body weight, exercising regularly, using joint protection techniques when lifting heavy objects, and eating a nutritious diet.