A unicondylar knee implant system according to one embodiment includes a unicondylar femoral knee component having a single sagittal radius, a tibial bearing component, and a tibial tray component having a self-locking keel. The unicondylar knee implant system also provides for a locking mechanism for securing the tibial bearing component onto the tibial tray component. The unicondylar knee system allows for a simplified surgical technique, complete interchangeability between sizes, and a more MIS compatible implant system.