Arthritis is inflammation of one or more of your joints. The main symptoms of arthritis are joint pain and stiffness, which typically worsen with age. The two most common types of arthritis are osteoarthritis and rheumatoid arthritis. Osteoarthritis is usually caused by normal wear and tear, while rheumatoid arthritis is an autoimmune disorder. Other types of arthritis can be caused by uric acid crystals, infections or even an underlying disease, such as psoriasis or lupus. Treatments vary depending on the type of arthritis. The main goals of arthritis treatments are to reduce symptoms and improve quality of life.