A knee prosthesis includes a tibial component, a bearing and a femoral component. The tibial component includes a platform and at least one rib extending upwardly and forwardly, a front edge of upper surface of the platform is provided with at least one front lug boss, and back edge of the upper surface of the platform is provide with at least one back lug boss. The lower surface of the bearing is provided with a groove matching with the at least one rib, a front slot matching with the front lug boss and a back slot; the femoral component is articulated with the bearing; at least one rib is provided with a medial wall and a lateral wall, one of the them is provided with a bent portion and formed with a first inclined surface which extends in a direction away from the other one.