Gout is a type of arthritis caused by uric acid crystals in your joints and other tissues. Your body normally creates uric acid as it breaks down purines. Purines are found in some foods and drinks. Normally, your kidneys filter uric acid out of your blood. However, if you have gout, your kidneys do not eliminate enough uric acid through urination. The most commonly affected area is the big toe joint, but other parts of the foot and body (such as the knees, wrists and elbows) can also be affected. Gout is the most common form of inflammatory arthritis in men older than 40.