Pigmented villonodular synovitis of the knee in a patient with Paget's disease of the adjacent femoral bone.

A 49-year-old male patient, diagnosed as having Paget's disease involving the lumbar vertebrae and both femora, felt persistent pain and swelling in the left knee after trauma. A synovectomy was performed. Clinical and histological findings led to the diagnosis of pigmented villonodular synovitis of the knee joint. Only one previous case of this association has been reported. A common aetiology for both diseases is discussed, and traumatic factors should be considered in the aetiology of the association.