Source of infection: Most cases are believed to be hematogenous but traumatic inoculation is possible.
Usually a single joint is involved. Less often 2 or more joints may be affected.
An affected joint is:
(1) swollen with effusion
(2) painful on motion
(3) may develop a draining sinus
Joints most often affected:
(1) knee
(2) ankle
(3) elbow
(4) hand
Other findings:
(1) cutaneous infection is usually absent
(2) in an immunocompetent patient extra-articular involvement is uncommon
(3) tenosynovitis may develop, with some patients developing the carpal tunnel syndrome
Imaging studies show degenerative change with or without evidence of osteomyelitis.
Bacterial cultures are negative. Fungal culture of biopsy material may be necessary for diagnosis.
A biopsy will chronic inflammation with noncaseating granulomas. Organisms are often difficult to find.
The patient may be misdiagnosed pigmented villonodular synovitis, rheumatoid arthritis or other joint condition. However, the patient will not respond as expected to appropriate therapy.
Systemic findings with involvement of sites other than joints indicates disseminated disease.
