Introduction: A synovial chondromatosis is a rare benign neoplasm on the synovium. Although described as a benign disease, it can be very destructive and can cause severe osteoarthritis and pain. This is the first case encountered by us with such a degree of osteoarthritis and got treated by a total knee arthroplasty. Case presentation: A 55 year old man presented with right knee pain and repeated effusion caused by diffuse intra–articular and extra–articular synovial chondromatosis. He underwent careful preoperative imaging and planning followed excision of the loose fragments with total knee replacement and synovectomy in order to completely eradicate the disease. He has regained full range of movement and is free of his symptoms. Conclusions: Although synovial chondromatosis is described as a benign disease, it can be very destructive and debilitating. A challenging management dilemma arises when confronted with both synovial chondromatosis and osteoarthritis.