A form of arthritis, gout is characterized by sudden pain, redness, swelling, and stiffness, usually in the large joint of the big toe. Gout can also occur in the foot, ankle, or knees. and is caused by too much uric acid (UA) in the body, which can form hard crystals in joints. Attacks can last days or weeks, and may be treated with anti–inflammatories or UA–lowering medication. Talk to your doctor about diet changes that help break down UA.