Knee cancer surgery. Artwork showing a stage in the surgical treatment of a knee cancer using a Modular Universal Tumour And Revision System (MUTARS) interim prosthesis. The cancer is at the base of the femur (thigh bone) at upper left. Here, the internal muscle, bone and fat layers are shown, along with the blood vessels (red and blue) and nerves (yellow). The veins and arteries supplying the area being operated on have been tied off, and a retractor (upper left) is being used to hold back the thigh muscles from the bone. A black dotted line indicates an incision that will be made across the calf muscle tendon.