352 patients scheduled to undergo total knee arthroplasty for osteoarthritis were randomly allocated to receive either a mobile-bearing or fixed-bearing posterior-stabilized TKA, with further randomization into patella resurfacing or retention groups. The purpose of the study was to determine how mobile-bearing TKA implants compare to fixed-bearing implants in terms of lateral release rates. The lateral release rate results were the same between both types of implants, however, patellar resurfacing resulted in lower rates of lateral release as compared to patellar retention.