More than 50 million Americans have arthritis, a term that encompasses more than a hundred types of joint diseases and conditions. One of the most common is osteoarthritis, which usually occurs with age and may affect knees, hips, neck, lower back and fingers but sometimes follows an injury. Inflammatory arthritis, which includes rheumatoid arthritis, and gout are other common types. Symptoms of arthritis may include stiffness, redness, heat, swelling and pain. You may also have a fever, lose weight or get a rash or itch.