We present the histological findings of an extensor mechanism allograft which was used in a total knee arthroplasty two years after implantation. Analysis of the graft was undertaken at four distinct anatomical levels and it was found to be incorporated into host tissue at each level. A wedge of fibrinoid necrosis, probably related to impingement of the graft on the tibial polyethylene insert, was seen. Impingement may play a role in the injury and necrosis of an allograft and may be one mode of failure in an extensor mechanism allograft.

1. An unusual case of haemangiomatosis in an adult is presented. The association of angiomatosis with massive osteolysis and With extensive soft-tissue destruction is discussed.

2. The extensive vascular involvement of skin, soft tissues and bone strengthens the idea that massive osteolysis results from vascular proliferation or angiomatosis.