Gout vs pseudogout: two crystal arthritis conditions compared

Gout and pseudogout are both crystal arthritis. In each, tiny crystals form or shed in a joint and the body reacts with intense inflammation. In gout the crystals are made of urate and are linked to a high level of uric acid in the blood. In pseudogout, the name meaning false gout, the crystals are calcium pyrophosphate. The attacks feel similar, which is how the name arose, but the usual joints, the people affected, the tests and the long-term treatments differ.

A first attack in a big toe in a middle-aged or older man points towards gout. A swollen, painful knee, wrist or shoulder in someone over 60, particularly after illness or surgery, points towards pseudogout. These are tendencies rather than rules, and the only reliable way to be sure is to find the crystals in a sample of joint fluid.

The NHS describes gout as a type of arthritis causing sudden, severe joint pain, usually in the big toe but also in other joints in the feet, ankles, hands, wrists, elbows or knees, with hot, swollen, red skin over the joint. It is caused by too much uric acid in the blood, which can lead to crystals forming around the joints. Risks include being overweight, drinking alcohol, taking certain medicines such as diuretics, and conditions such as high blood pressure, kidney problems and diabetes. Triggers include illness with a high temperature, heavy drinking or a very large meal, dehydration, joint injury and certain medicines.

Gout attacks are usually treated with an NSAID such as ibuprofen, with steroids as tablets or injection if that does not help. People with frequent attacks or high uric acid may need uric acid-lowering medicine, which the NHS says should be taken regularly even when there are no symptoms. Repeated untreated attacks can lead to joint damage, tophi (hard lumps under the skin) and kidney stones.

Arthritis UK explains that calcium crystals occur naturally in the body and many people have them in joint cartilage for years without trouble. Sometimes the crystals shake loose into the joint cavity, which causes painful inflammation and swelling. Increasing age raises the likelihood, and certain conditions are linked, including an overactive parathyroid gland, too much iron in the body (haemochromatosis) and, more rarely, low magnesium. People with osteoarthritis, particularly in the knee, often have calcium crystals in the cartilage.

An attack may be triggered by an injury, an illness that causes a fever such as flu or a chest infection, or a major stress on the body such as an operation or a heart attack. Often it is not clear why the crystals shed. Symptoms usually settle on their own, but treatment can ease the pain: draining fluid from the joint and injecting a steroid, ice packs, NSAIDs, colchicine (best started within 24 hours of the attack) or steroids when the others cannot be used.

Arthritis UK says acute CPP crystal arthritis can look very similar to gout or a joint infection, and the NHS warns about infection in a painful swollen joint, so infection is something a doctor will want to exclude. The NHS says that for gout a GP may measure uric acid in the blood and, if that is unclear, refer to a rheumatologist, who may take fluid from the affected joint with a thin needle; if that cannot be done or is unclear, a scan is arranged. Arthritis UK describes tests for acute CPP crystal arthritis that include testing joint fluid for crystals or infection, X-rays and ultrasound to look for calcium in the cartilage, and blood tests for inflammation, minerals, infection and kidney problems.

Arthritis UK points out that the crystals may be small and difficult to find and that many people have calcium crystals in their cartilage for years without problems, so a blood result or X-ray alone may not settle the question. Examining joint fluid for crystals is the test that looks for the crystal directly.

The NHS says to ask for an urgent GP appointment or contact NHS 111 if you have a sudden pain and swelling in a joint that is getting worse, with a very high temperature or feeling hot, cold or shivery, or you feel sick or cannot eat, as these could mean an infection inside the joint. The same applies whichever crystal arthritis you suspect. See a GP if you have symptoms of gout for the first time or your usual treatments are not helping.