Rheumatoid Arthritis Flare Presenting as Prosthetic Joint Infection With Synovial Next Generation Sequencing Guiding Treatment: A Case Report.

A patient with rheumatoid arthritis (RA) experienced a flare that mimicked a prosthetic joint infection several years after undergoing total knee arthroplasty. She presented with gradual worsening knee pain following discontinuation of her RA medication. Elevated inflammatory markers and an increased synovial cell count were noted, but synovial fluid polymerase chain reaction testing was negative. A nonoperative treatment approach was chosen, and she resumed her RA medication which led to symptom resolution. Next-generation sequencing played a pivotal role in ruling out infection and identifying the rheumatic cause of the knee pain, thereby avoiding unnecessary revision surgery. Next-generation sequencing may be a valuable diagnostic tool in clinically ambiguous cases.