Partial knee replacement surgery. Clip 29 of 48. Close-up of surgeons operating on the knee of a patient undergoing a partial knee replacement. This is called unicompartmental arthroplasty (UKA). UKA involves replacing just one of the three knee compartments, rather than the whole knee. It is usually carried out to treat osteoarthritis or injury of that knee compartment. The knee is accessed through an incision that is smaller than that for a total knee replacement. Bone and tissue is removed using clippers, drills, hammers and saws. Implants are added and secured in place, and the wound is then closed with sutures. For the entire sequence, see clips K003/0052 to K003/0099.