A rare case of extensive diffuse nonpigmented villonodular synovitis as a cause of total knee arthroplasty failure

INTRODUCTIONNonpigmented villonodular synovitis (non-PVNS) is a benign proliferative disease involving the synovium. It is a rare condition that is little recognized. Non-PVNS has been reported as a cause of total knee replacement failure.PRESENTATION OF CASEWe report a case of extensive diffuse non-PVNS in a patient with tibial component loosening after total knee replacement and review the related literature.DISCUSSIONIt is reported that pigmented villonodular synovitis (PVNS) occurs less frequently than non-PVNS after knee replacement. However, there are many more case reports of PVNS than non-PVNS after knee arthroplasty in the English-language literature.CONCLUSIONPreviously, there were no reported cases of extensive diffuse non-PVNS after total knee arthroplasty (TKA). This case study highlights an unusual case of non-PVNS as a cause of TKA failure. We propose that non-PVNS should be considered as a differential diagnosis in patients after TKA who present with recurrent pain and effusion/hemarthrosis of the knee, and that it is one of the causes of implant loosening after TKA.