This study characterized the footstep pattern and knee kinematics during walking in 12 patients who had undergone unicompartmental knee arthroplasty for unilateral medial compartment osteoarthritis. Patients had all achieved a successful recovery and were tested at least 1 year after surgery. Gait analysis was conducted during self-selected comfortable and fast walking conditions using a 3-dimensional motion analysis system and electronic walkway. Results showed that patients were able to increase their walking speed by 28% by increasing both stride length and cadence. All but one patient showed a biphasic pattern of flexion-extension motion about the treated knee. In 8 of 12 patients, significant increases in knee flexion were seen in the treated limb compared with the contralateral limb, the cause and ramifications of which are yet to be determined.