Gout, a form of arthritis found in any joint including the knee, is caused by too much uric acid, reports WebMD. Too much uric acid in the blood causes crystals to form, ultimately causing pain. Certain medications, being overweight and eating certain foods can be triggers of gout flares.
Urate crystals, which are sharp structures formed from too much uric acid, can accumulate in the knee joint and surrounding tissues, causing a flare of pain symptoms and swelling, states Mayo Clinic. Risk factors that increase a person's chances of developing gout include being male, being overweight and having a family history of gout, according to WebMD.
Medications can also increase the risk of developing gout, reports WebMD. Patients who take a daily aspirin or are on chemotherapy drugs face an increased risk of gout. Diuretics can also contribute to gout flares.
Doctors often suggest that patients diagnosed with gout modify their diets to eliminate gout-triggering foods, such as alcohol, seafood, liver and other organ meats with high levels of purine, a chemical the body breaks down into uric acid. Foods lower in purines, which may help reduce the risk of developing gout, include tomatoes, low-fat milk and green vegetables, states WebMD.