A tibial prosthesis comprising: a distal surface; a proximal surface generally opposite said distal surface, said proximal surface having a lateral compartment and a medial compartment; and a peripheral wall extending between said distal and said proximal surface, said peripheral wall defining: an anterior edge; a lateral posterior edge generally opposite said anterior edge and forming a posterior boundary of said lateral compartment; a medial posterior edge generally opposite said anterior edge and forming a posterior boundary of said medial compartment; a lateral periphery extending from said anterior edge to said lateral posterior edge, said lateral periphery defining a plurality of adjacent lateral arcs (208, 210, 212, 214, 216) and a medial periphery extending from said anterior edge to said medial posterior edge, said medial periphery defining a plurality of adjacent medial arcs (220, 222, 224), characterised by an adjacent pair of said plurality of adjacent lateral arcs defining a first lateral radius and a second lateral radius, respectively, said first lateral radius larger than said second lateral radius by at least 100%; and an adjacent pair of said plurality of adjacent medial arcs defining a first medial radius and a second medial radius, respectively, said first medial radius larger than said second medial radius by less than 75%. a distal surface; a proximal surface generally opposite said distal surface, said proximal surface having a lateral compartment and a medial compartment; and a peripheral wall extending between said distal and said proximal surface, said peripheral wall defining: an anterior edge; a lateral posterior edge generally opposite said anterior edge and forming a posterior boundary of said lateral compartment; a medial posterior edge generally opposite said anterior edge and forming a posterior boundary of said medial compartment; a lateral periphery extending from said anterior edge to said lateral posterior edge, said lateral periphery defining a plurality of adjacent lateral arcs (208, 210, 212, 214, 216) and a medial periphery extending from said anterior edge to said medial posterior edge, said medial periphery defining a plurality of adjacent medial arcs (220, 222, 224), characterised by an adjacent pair of said plurality of adjacent lateral arcs defining a first lateral radius and a second lateral radius, respectively, said first lateral radius larger than said second lateral radius by at least 100%; and an adjacent pair of said plurality of adjacent medial arcs defining a first medial radius and a second medial radius, respectively, said first medial radius larger than said second medial radius by less than 75%. an anterior edge; a lateral posterior edge generally opposite said anterior edge and forming a posterior boundary of said lateral compartment; a medial posterior edge generally opposite said anterior edge and forming a posterior boundary of said medial compartment; a lateral periphery extending from said anterior edge to said lateral posterior edge, said lateral periphery defining a plurality of adjacent lateral arcs (208, 210, 212, 214, 216) and a medial periphery extending from said anterior edge to said medial posterior edge, said medial periphery defining a plurality of adjacent medial arcs (220, 222, 224), characterised by an adjacent pair of said plurality of adjacent lateral arcs defining a first lateral radius and a second lateral radius, respectively, said first lateral radius larger than said second lateral radius by at least 100%; and an adjacent pair of said plurality of adjacent medial arcs defining a first medial radius and a second medial radius, respectively, said first medial radius larger than said second medial radius by less than 75%.