Total Knee Arthroplasty in a patient with anti-synthetase syndrome and severe knee stiffness: A case report.

Anti-synthetase syndrome (ASyS) is a rare autoimmune disorder with diverse clinical manifestations, often initially misdiagnosed as rheumatoid arthritis. Delayed diagnosis may result in severe joint destruction, disabling polymyositis, and even mortality from rapidly progressive respiratory illness. With this context, we present a rare case of ASyS in a 53-year-old female exhibiting the classical triad of chronic arthritis, myositis, and interstitial lung disease (ILD) - features seldom observed together. She experienced severe arthritis in both knees with pronounced varus deformity, impairing her daily functional, vocational, and recreational activities; therefore, Total Knee Arthroplasty (TKA) was performed. To our knowledge, this is the first reported case of TKA in a patient with ASyS, illustrating the extent of large-joint involvement and the scarcity of literature on its surgical management.