Gout-induced arthropathy after total knee arthroplasty: a report of two cases.

Gout, although relatively rare in joint replacements, can present as an acute or chronic painful knee or hip arthroplasty. Gout and acute infection of a joint replacement can be difficult to differentiate, with the physical examination and laboratory study results frequently being similar. Both conditions can present with a rapid onset of joint pain, swelling, erythema, and constitutional symptoms, including fevers and malaise. Laboratory findings in both conditions often include an elevated leukocyte count, erythrocyte sedimentation rate, and C-reactive protein level. Negatively birefringent, needle-shaped crystals in the synovial fluid confirm the diagnosis of gout. The mistaken diagnosis of septic arthritis in a joint replacement with crystal-induced synovitis can lead to inappropriate open debridement or component removal. The current study includes a review of the literature and presents two cases of gout after total knee arthroplasty. These cases suggest that in situations of suspected sepsis without synovial fluid crystals, operative intervention is indicated with a presumed diagnosis of septic arthritis. The identification of chalky white or yellow deposits in the synovium or bone is highly suggestive of gout. The definitive diagnosis is made by polarized light histologic evaluation of these tissues. If these deposits are present in the absence of a positive preoperative culture, positive Gram stain for bacteria, or component loosening, component retention is indicated.