Partial knee replacement (PKR) is a surgical procedure in which a part of the arthritic knee is replaced. It can be unicondylar knee arthroplasty (UKA) or a patellofemoral arthroplasty (PFA). UKA can be further classified into medial or lateral condylar arthroplasty. This chapter describes the various indications, contraindications, implant types, advantages and complications of the surgery.