Gout is a condition that causes painful swelling in the joints and is caused by a build up of uric acid in the blood. The body usually rids itself of uric acid when we pass urine, but if it builds up, crystals can form and collect in a joint, causing inflammation, swelling and pain.
The base of the toe is the most commonly affected joint and the pain can be severe, making walking very painful. The joint affected will normally swell and the surrounding skin may look red and inflamed. Gout is treated with medication and can be controlled through changes in diet and reducing alcohol consumption.
Source: NHS choices