Joint prosthesis

A joint prosthesis comprising:

• a femoral component which includes a pair of laterally spaced apart condyles each of which is cured generally to be similar to the shape of an anatomical femoral condyle, the surface of each said condyle being defined at least in part by (a) anterior posterior radii R.sub.CF and R.sub.CE, wherein R.sub.CF is the radius of curvature of that portion of the condyle which is weight bearing in flexion and R.sub.CE represents that portion of the curvature of the condyle which is weight bearing in extension, and (b) a medial lateral radius R.sub.CML ;
• and
• a tibial component, at least the upper portion of which is made of a plastic material and includes a pair of laterally spaced apart concavities, each of which is adapted to receive one of the condyles of the femoral component, the surfaces of such concavities being defined by an anterior posterior radius R.sub.TAP and a medial lateral radius R.sub.TML,
• wherein said condyles and concavities are formed such that the ratio R.sub.CML /R.sub.TML is about 0.96 and the ratio of R.sub.CE /R.sub.TAP is between 0.60 and 0.075.