Knee arthroplasty has become one of the most successful standard procedures in orthopaedic surgery. With a more frequent use in young and active patients bone-saving procedures have become more important. The goal is to save good bone stock for the revision procedure. Therefore, unicompartmental knee arthroplasty is a good example. Instrumentation and minimally invasive surgical techniques have been improved so very good long-term results and early functional results are achieved. The paper describes the surgical technique with true capsule incision and extramedullary alignment technique. In a prospective study, the early functional results with the ZUK implant were excellent. The implant may not be indicated for every knee situation and an exact differential indication and sound surgical technique are necessary. Its use, however, in cases with unicompartmental knee arthritis, contributes to excellent early rehabilitation and to maintaining autologous bone. Therefore, the minimally invasive unicompartmental knee arthroplasty is a sensible alternative to other options.