When gout causes severe joint pain, it is called a gout attack, a gout flare-up, or acute gout. Pain is typically accompanied by extreme joint tenderness, swelling, warmth, and skin redness. The symptoms may come on suddenly and without warning.
Experts estimate gout will affect 4% of Americans during their lifetimes, and often occurs in men and people over age 60.1 Typically, only one joint is affected at a time, but it is possible to have several joints affected during a gout attack.
Joints Affected by Gout
Gout can affect any joint, but some joints are more likely to be affected than others. Joints commonly affected include the big toe, the foot’s instep, heel, ankle, and knee.2 Less often, gout affects the elbow, wrist, fingertips, or spine.2-7
Differences between men and women
Sex differences play a role in which joints are affected:
- In men, about 85% of gout flare-ups affect joints in the lower extremities. About 50% of first-time gout attacks involve a big toe joint.8
- In women, a gout attack is most likely to occur in a knee.10 In addition, women may be more likely to get gout in the upper extremities.9
While women are less likely to get gout, they are more likely to have multiple joints affected by gout.13
How a Gout Flare-Up Develops
Gout results from a build-up of uric acid crystals (monosodium urate crystals) in a joint. These needle-like, microscopic crystals collect in the soft tissue of a joint, causing pain that can be excruciating, as well as swelling, redness, and warmth.
How uric acid crystals form
The build-up of uric acid crystals begins with purines, a chemical compound found in many foods.
- When the body metabolizes purines, it produces a substance called uric acid.
- The uric acid enters the bloodstream.
- The kidneys filter the blood and normally filter out excess uric acid. This uric acid is then excreted via urine (70%) or stool (30%).10
- If the kidneys cannot adequately filter out excess uric acid, or if the body produces too much uric acid, there will be too much uric acid in the bloodstream.
- Too much uric acid in the bloodstream is called hyperuricemia.
- In some people, hyperuricemia leads to the formation of uric acid crystals that collect in joint tissue, leading to painful symptoms.
An inability to adequately process and excrete uric acid accounts for an estimated 90% of gout cases.9 Other cases occur because a body produces too much uric acid.
Read more about Hyperuricemia - High Uric Acid Levels and Gout
Why Flare-Ups Happen at Night
It is not uncommon for gout to flare-up in the middle of the night, waking a person from a sound sleep. One research study of more than 700 gout patients found that flare-ups were 2.4 times more likely between midnight and 8 am than between 8 am and 4 pm.11
Researchers theorize gout attacks often occur at night because:
- Uric acid is more likely to form crystals at lower temperatures. The body’s temperature drops slightly during sleep, encouraging the formation of crystals.12,13
- Breathing rates slow down during sleep, and the lungs expel less carbon dioxide. Excess carbon dioxide can cause the blood to become slightly more acidic. This condition, called respiratory acidosis, may encourage the formation of uric acid crystals.14
- People with sleep apnea take in less oxygen, which can lead to an increase in the body’s production of purines and cause hyperuricemia.15,17
- The body’s cortisone levels tend to dip while sleeping. Cortisone suppresses inflammation, and a dip in cortisone may contribute to gouty inflammation.16,17
- Overnight dehydration may facilitate hyperuricemia and/or increase the concentration of crystals in the joint fluid.17,
More research is needed in this area.
Gout Attack vs. Chronic Gout
It is possible to have a gout flare-up and never experience another. Repeated instances of acute gout are called chronic gout17.
The treatment goals for a gout attack are different than those for chronic gout. When treating a gout attack, the goal is to relieve pain and inflammation. When treating chronic gout, the goal is to prevent future gout attacks and long-term joint damage.
While some people with chronic gout may get frequent gout attacks, others may have years in between attacks. If chronic gout is not treated, attacks may become more frequent and/or last longer.
Left untreated, a gout attack will usually resolve itself within a few days or weeks. Chronic gout can permanently damage a joint’s tissues and decrease its range of motion. For this reason, it is important to recognize symptoms, understand risk factors, get an accurate diagnosis, and treat and prevent gout.