A tibial insert comprising: a lateral articular surface configured to articulate with a lateral condyle of a femoral component and including an arcuate articular path extending in an anterior-posterior direction, wherein the arcuate articular path is defined by a plurality of points on the lateral articular surface and, when the tibial insert is viewed in a cross-sectional medial-lateral plane at each point, each point defines a distal-most point of the lateral articular surface in the corresponding cross-sectional medial-lateral plane, and wherein the lateral articular surface has a cross-sectional concave curvature orthogonal to the arcuate articular path , the cross-sectional concave curvature being uniform at each of the plurality of points; a medial articular surface configured to articulate with a medial condyle of the femoral component , wherein the medial articular surface is asymmetrically shaped relative to the lateral articular surface and has a coronal concave curvature that is non-uniform in the anterior-posterior direction; and wherein the arcuate articular path when viewed in a cross-section along the arcuate articular path has a curvature that includes a semi-planar section , an anterior curved section located anterior of the semi - planar section, wherein the semi-planar section defines a lateral dwell region that defines a distal-most area of the lateral articular surface ; characterized in that the curvature of the arcuate articular path when viewed in a section along the arcuate articular path further comprises a plurality of posterior curved sections (2002; 2004) located posterior of the semi-planar section . a lateral articular surface configured to articulate with a lateral condyle of a femoral component and including an arcuate articular path extending in an anterior-posterior direction, wherein the arcuate articular path is defined by a plurality of points on the lateral articular surface and, when the tibial insert is viewed in a cross-sectional medial-lateral plane at each point, each point defines a distal-most point of the lateral articular surface in the corresponding cross-sectional medial-lateral plane, and wherein the lateral articular surface has a cross-sectional concave curvature orthogonal to the arcuate articular path , the cross-sectional concave curvature being uniform at each of the plurality of points; a medial articular surface configured to articulate with a medial condyle of the femoral component , wherein the medial articular surface is asymmetrically shaped relative to the lateral articular surface and has a coronal concave curvature that is non-uniform in the anterior-posterior direction; and wherein the arcuate articular path when viewed in a cross-section along the arcuate articular path has a curvature that includes a semi-planar section , an anterior curved section located anterior of the semi - planar section, wherein the semi-planar section defines a lateral dwell region that defines a distal-most area of the lateral articular surface ; characterized in that the curvature of the arcuate articular path when viewed in a section along the arcuate articular path further comprises a plurality of posterior curved sections (2002; 2004) located posterior of the semi-planar section . <EOS>