Objective To study the effects of different posterior slope installations of unicompartmental knee arthroplasty (UKA) prostheses on the loading and motion of the knee joint and insert wear. Methods A combined approach involving The UKA musculoskeletal multibody dynamic, finite element, and wear prediction models was used to investigate the effects of five different posterior slope installation positions of the UKA prosthesis on the postoperative knee joint force and motion, insert contact stress, linear wear depth, and wear volume. Results At a 0° posterior slope, the maximum von Mises stress of the insert was 24.84 MPa, maximum contact stress was 47.61 MPa, and volumetric wear after 5 million cycles (MC) was 47.29 mm3. As the posterior slope angle of the UKA prosthesis increased, the internal rotation and posterior translation during the gait cycle increased, the medial joint force during the swing phase increased, the von Mises and contact stresses of the insert after 5 MC decreased significantly, and the wear area, maximum linear wear depth, and volumetric wear volume of the insert were consequently reduced. Compared to the 0° posterior slope, the linear wear depths of the insert at the 3°, 5°, and 7°posterior slopes decreased by 17.8%, 19.2%, and 20.6%, respectively. The volumetric wear volumes of the inserts decreased by 24.5%, 30.9%, and 34.3%, respectively. Conclusion Installing a UKA prosthesis with a posterior slope exceeding 3° significantly increases internal rotation and posterior translation during the gait cycle, further reducing the articular volumetric wear of the polyethylene insert.