A prosthetic knee joint comprising: a single piece tibial component comprising an asymmetric lateral dished surface defining a first arc projected onto a sagittal plane and an anteriorly-elevated medial dished surface, comprising an external rotation axis and anteriorly elevated with respect to said lateral dished surface, said medial dished surface defining a second arc projected onto the sagittal plane wherein said first arc has a greater radius than a said second arc, and posterior portions of said lateral dished surface and said medial dished surface each defined by single arcs of constant radius projected on a frontal plane, said single piece tibial component further comprising a protrusion located between said lateral dished surface and said anteriorly elevated medial dished surface, anterior portion of said protrusion defining an anterior ramp and posterior portion of said protrusion defining a posterior ramp, said medial dished surface further comprising an external rotation axis; a single piece femoral component comprising asymmetric lateral and medial condylar shaped surfaces, an anterior femoral groove, and a cupola located between said lateral and medial condylar surfaces, said cupola being a continuation of said femoral groove,; said lateral condylar shaped surface is in sliding contact with said lateral dished surface and operatively configured to posteriorly displace a first distance, with respect to said lateral dished surface, in response to increasing flexure, said medial condylar shaped surface is in sliding contact with said medial dished surface and operatively configured to displace a second distance lesser than said first distance, with respect to said medial dished surface, in response to increasing flexure, wherein said displacements result in rotation of said femoral component with respect to said tibial component about said external rotation axis and, for angles of flexion within a specified range, a surface of said cupola is in contact, and conformal with said posterior ramp; said lateral and said medial condylar surfaces and said posterior ramp and said surface of cupola are respectively configured to maintain contact as said lateral condylar surface displaces posteriorly, with respect to said external rotation axis, in concert with flexure. a single piece tibial component comprising an asymmetric lateral dished surface defining a first arc projected onto a sagittal plane and an anteriorly-elevated medial dished surface, comprising an external rotation axis and anteriorly elevated with respect to said lateral dished surface, said medial dished surface defining a second arc projected onto the sagittal plane wherein said first arc has a greater radius than a said second arc, and posterior portions of said lateral dished surface and said medial dished surface each defined by single arcs of constant radius projected on a frontal plane, said single piece tibial component further comprising a protrusion located between said lateral dished surface and said anteriorly elevated medial dished surface, anterior portion of said protrusion defining an anterior ramp and posterior portion of said protrusion defining a posterior ramp, said medial dished surface further comprising an external rotation axis; a single piece femoral component comprising asymmetric lateral and medial condylar shaped surfaces, an anterior femoral groove, and a cupola located between said lateral and medial condylar surfaces, said cupola being a continuation of said femoral groove,; said lateral condylar shaped surface is in sliding contact with said lateral dished surface and operatively configured to posteriorly displace a first distance, with respect to said lateral dished surface, in response to increasing flexure, said medial condylar shaped surface is in sliding contact with said medial dished surface and operatively configured to displace a second distance lesser than said first distance, with respect to said medial dished surface, in response to increasing flexure, wherein said displacements result in rotation of said femoral component with respect to said tibial component about said external rotation axis and, for angles of flexion within a specified range, a surface of said cupola is in contact, and conformal with said posterior ramp; said lateral and said medial condylar surfaces and said posterior ramp and said surface of cupola are respectively configured to maintain contact as said lateral condylar surface displaces posteriorly, with respect to said external rotation axis, in concert with flexure.