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 most common types of arthritis are osteoarthritis and rheumatoid arthritis.
Osteoarthritis causes cartilage — the hard, slippery tissue that covers the ends of bones where they form a joint — to break down. Rheumatoid arthritis is an autoimmune disorder that first targets the lining of joints (synovium).
Uric acid crystals, infections or underlying disease, such as psoriasis or lupus, can cause other types of arthritis.