Unicompartmental knee arthroplasty is a bone-preserving and more physiological alternative to total knee arthroplasty in selected patients with isolated medial or lateral compartment osteoarthritis. Its historical development began with the isolated tibial condyle replacement procedures of MacIntosh and Hunter and evolved through McKeever tibial plateau prostheses, the St. Georg Sled, Marmor, and Insall designs into the modern concept of unicompartmental knee replacement. One of the major milestones in this field was the Oxford unicompartmental knee prosthesis developed by Goodfellow and O’Connor. Based on the mobile-bearing principle, this design aimed to reduce polyethylene wear and preserve natural knee kinematics by providing a broad contact area between the femoral condyle and the tibial component. The success of unicompartmental knee arthroplasty depends on several factors, including implant geometry, bearing design, articular conformity, polyethylene thickness, fixation method, and surgical accuracy. Fixed-bearing designs offer technical simplicity and a lower risk of bearing dislocation, whereas mobile-bearing systems may provide reduced contact stress and improved surface conformity. Cemented and cementless designs differ not only in the use of bone cement but also in macro-geometry, surface technology, osseointegration potential, and load-transfer biomechanics. Contemporary cementless systems aim to enhance biological fixation through porous metal structures and hydroxyapatite coatings. Therefore, implant selection should be individualized according to patient characteristics, implant design principles, and the surgeon’s experience.