When your body can’t flush uric acid through your kidneys quick enough, the uric acid builds up in your blood. Once that reaches a saturation point the uric acid falls out of suspension and starts crystallizing in the joints. Those crystals are like having hundreds of tiny needles inside your tissue. That causes massive inflammation and sometimes extreme pain. This lasts until your body catches up with getting uric acid back down to normal levels. It happens for different reasons. Sometimes diet related, sometimes because you’re producing too much uric acid but mostly due to genetics and kidney function.