A knee prosthesis for unicompartmental implantation into a knee joint is implantable without requiring bone resection and includes a body free of any means of fixation to a portion of knee joint, anatomy and having a substantially elliptical shape in plan and a pair of contoured opposed faces including a convex face and a concave face. A peripheral edge extends between the faces and includes a first side, a second side opposite the first side, a first end and a second end opposite the first end. A first dimension D is defined by the first end and the second end. A second dimension F is defined by the first side and the second side. The dimension F is from about 0.25 to about 1.5 of the dimension D.