The authors treated 24 patients with total knee arthroplasty who had a massive allograft used to reconstruct the knee and who later had instability, degeneration, or a fracture near the articular surface of the graft develop. Patients then were followed up for a minimum of 2 years and a mean of 8.2 years. Overall, 96% of the patients retained a functional limb, although 46% underwent revision surgery, and an additional 12% had some other major complication. Statistical analysis showed a significant negative effect of chemotherapy on revision-free survival of the prosthesis. Patients with high-grade tumors were at significantly greater risk of fracture of the allograft-prosthesis composite. Certain technical factors were identified that seemed to predispose the allograft-prosthesis reconstructions to early failure. Total knee arthroplasty can be used to treat patients with complications of massive osteoarticular allografts and may prolong the functional life of an otherwise successful limb salvage reconstruction.