Gout - also known as metabolic arthritis, occurs due to high level of uric acid in the body. This acid is waste product of human body and normally body exclude it by kidneys through urin. In the cases of excess it accumulates in the joints assuming the form of crystals. It causes inflammation including pain, swelling and tenderness.
In the most cases this kind of arthritis affects big toe, but it can also occur in knee, foot, ankle, hand, wrist and elbow. Also it affect man (between 30 and 50 years) more oftenly then women.
Symptoms can be described as very sudden and strong attacks of pain and tenderness, warmth, redness and swelling in the joints. First attack of Gout usually occurs at night. This attacks may occur oftenly in patients who eat to much of certain foods, have some recent surgery, drink too much alcohol, had some joint injury, have strong diets and in patients having chemotherapies.
Gout can be diagnosed by physical exam and mediacl history or by testing blood or joint fluid.
Treatments options include diet, proper medications and if those methods do not help surgery may be necessary.

Chronic gout with tophi on elbow and knee (taken from Wikipedia).