Abstract

A joint effusion is the presence of increased intra-articular fluid. It may affect any joint. Commonly it involves the knee.

Diagnostic approach

The approach to diagnosis depends on the joint involved. While aspiration of the joint is considered the gold standard of treatment, this can be difficult for joints such as the hip. Ultrasound may be used both to verify the existence of an effusion and to guide aspiration.

Diagnostic approach | Differential diagnosis

There are many causes of joint effusion. It may result from trauma, inflammation, hematologic conditions, or infections.

Diagnostic approach | Differential diagnosis | Septic arthritis

Septic arthritis is the purulent invasion of a joint by an infectious agent with a resultant large effusion due to inflammation.

Diagnostic approach | Differential diagnosis | Gout

Gout is usually present with recurrent attacks of acute inflammatory arthritis (red, tender, hot, swollen joint). It is caused by elevated levels of uric acid in the blood that crystallizes and deposits in joints, tendons, and surrounding tissues. Gout affects 1% of individuals in Western populations at some point in their lives.

Diagnostic approach | Differential diagnosis | Trauma

Trauma from ligamentous, osseous or meniscal injuries can result in an effusion. These are often hemarthrosis or bloody effusions.