A-C, Radiographs of a 58-year-old man show malignant fibrous histiocytoma in proximal tibia. D, Incision as outlined includes resection of the biopsy track. E, Medial flap is raised to expose vascular structures posteriorly. F, On the lateral side, the peroneal nerve is dissected and isolated from tumor. G, Intraarticular resection is done because joint is not involved. H, Proximal tibia has been removed, and medial head of gastrocnemius has been harvested for extensor mechanism reconstruction and coverage. I, Proximal tibial endoprosthesis. J, Patellar tendon is attached to the prosthesis. K, Medial gastrocnemius is rotated anteriorly and sutured to lateral fascia. L, Prosthesis is completely covered with soft tissue. M, Skin graft is required to complete closure. N and O, At one year after surgery, the patient has good range of motion and no extensor lag.