Arthritis, gout: Joint inflammation caused by uric acid crystal deposits in the joint space. An attack is usually extremely painful. The uric acid crystals are deposited in the joint fluid (synovial fluid) and joint lining (synovial lining). Intense joint inflammation occurs as white blood cells engulf the uric acid crystals, causing pain, heat, and redness of the joint tissues. The term "gout" commonly is used to refer to these painful arthritis attacks but gouty arthritis is only one manifestation of gout.