What happens in the joint
As we age, calcium pyrophosphate crystals accumulate in the cartilage and menisci. While they lie in the tissue, a person does not feel anything, and the finding on an x-ray can be accidental. But with injury, dehydration, surgery or serious illness, the crystals separate and enter the joint cavity. Cells in the synovium recognize them as foreign, release inflammatory molecules, and the joint quickly fills with fluid. The attack lasts from several days to two to three weeks and goes away even without treatment, but is repeated.
- Calcium pyrophosphate crystals are deposited in cartilage
- Chondrocalcinosis on x-ray may not give any complaints
- The release of crystals into the joint cavity triggers an attack
- Most commonly affected are the knee, wrist, shoulder, ankle
- Chronic arthritis may develop over time
Causes and risk factors
The main factor is age: after 60 years, the frequency of deposits increases every decade. In younger patients, the disease is often associated with metabolic disorders and requires additional examination. Hyperparathyroidism, hemochromatosis, low magnesium levels, chronic kidney disease and familial forms increase the risk. An attack is often triggered by surgery, joint injury, acute illness, dehydration, or a sudden change in therapy. A meat-restricted diet, which helps with gout, does not affect pyrophosphate arthropathy.
- Age over 60 years
- Previous injury or joint surgery
- Hyperparathyroidism and high calcium levels
- Hemochromatosis and iron overload
- Low magnesium levels
- Chronic kidney disease
- Familial forms in young patients
How is it different from gout?
Both diseases cause sudden acute arthritis, but the crystals are different. In gout, these are uric acid salts, the first metatarsophalangeal joint of the foot is most often affected, and the level of uric acid is usually elevated. In pseudogout, calcium crystals are present, the favorite targets are the knee and wrist, and uric acid is normal. X-rays of pseudogout show cartilage calcification. The only way to distinguish them is by examining the joint fluid under a polarizing microscope.
- Gout - uric acid crystals, pseudogout - calcium pyrophosphate
- Gout is most often in the foot, pseudogout - in the knee and wrist
- Uric acid is usually normal in pseudogout
- Chondrocalcinosis visible on x-ray
- Diet for pseudogout does not help
- The exact answer is given by analysis of synovial fluid
Diagnostics
The doctor's first task is to rule out suppurative arthritis, which looks very similar and requires immediate treatment. Therefore, in case of acute inflammation of a large joint, a puncture is performed: the fluid is sent for culture, cell counting and searching for crystals. Pyrophosphate crystals have a characteristic shape and glow differently in polarized light than urate crystals. X-rays of the joint show a fine line of calcification in the cartilage and menisci. Ultrasound reveals deposits and effusions. Blood tests help evaluate inflammation and find metabolic causes in young patients.
- Joint puncture with culture and search for crystals
- X-ray of the knee and wrist joints
- Ultrasound of the joint with assessment of effusion
- Complete blood count, ESR, C-reactive protein
- Uric acid for distinguishing from gout
- Calcium, magnesium, parathyroid hormone and ferritin in young people
Treatment and prevention of attacks
In the acute period, the joint is unloaded, cold is applied and anti-inflammatory drugs are prescribed. If they are contraindicated, colchicine or a short course of glucocorticoids are used, and if one large joint is affected, it is most effective to inject the hormone into the joint after ruling out infection. There is nothing to dissolve already formed crystals, so prevention is aimed at reducing the frequency of attacks: treatment of background metabolic disorders, sufficient drinking, correction of magnesium in case of its deficiency. If relapses occur frequently, your doctor may prescribe small doses of colchicine over a long period of time.
- Rest and cold on the joint in the first days
- Non-steroidal anti-inflammatory drugs as prescribed by a doctor
- Colchicine for contraindications to NSAIDs
- Intra-articular administration of glucocorticoid after exclusion of infection
- Treatment of hyperparathyroidism, magnesium deficiency, kidney disease
- Physical therapy and muscle strengthening outside of an attack
- Do not heat or rub the inflamed joint