Monoarthritis is inflammation (arthritis) of one joint at a time. It is usually caused by gout, pseudogout or septic arthritis. Rarer causes include familial Mediterranean fever (FMF).

Diagnosis

When faced with monoarthritis, one of the main decisions to make is whether to perform a joint aspirate by inserting a needle into the affected joint and removing some fluid for microscopic analysis. This decision is largely taken on inflammatory markers in blood tests (e.g. CRP), fever and the clinical picture. The main use of aspiration is to detect bacteria and neutrophil granulocytes (in septic arthritis) and crystals (crystal arthropathies).

Causes

Septic arthritis

Septic arthritis is due to a bacterial infection to the joint. It requires urgent antibiotic therapy.

Gout

In gout, the acute inflammatory arthritis is caused by excess uric acid caused by either overproduction or under-excretion. Before menopause, the incidence in males is higher than that in females, though the rates are equal postmenopause . Gout can cause mono- or polyarthritis, but usually results in monoarthritis first.

Pseudogout

When monoarthritis is caused by pseudogout (calcium pyrophosphate deposition disease, CPPD), the inflammation usually lasts days to weeks, and involves the knees in half of all attacks. Like gout, attacks can occur spontaneously or with physical trauma or metabolic stress. Patients may feel well in between pseudogout attacks attacks, and 5% present with pseudo-rheumatoid symptoms.

See also

• Gout
• Pseudogout
• Septic arthritis