Knee prosthesis

A knee prosthesis for a knee joint having a width (w), said knee prosthesis also having the width (w) and comprising a replacement femoral component (3) defining a medial ball-like condyle and a replacement tibial component (2) defining a cavity on a medial side corresponding to the medial ball-like condyle, said replacement femoral component (3) and replacement tibial component (2) defining a lateral compartment of the knee prosthesis, wherein:

• (i) the medial ball-like condyle (1) of the replacement femoral component (3) and the cavity (11) of the replacement tibial component (2) have a centre (Mb), a radius (Rb), a spherical surface (Sb), and define a Cartesian coordinate system X, Y, Z projecting from the replacement tibial component, said Cartesian coordinate system having its origin (0) at the centre (Mb);
• (ii) wherein the femoral component follows an articulate path within the lateral compartment defined by a trace-line (Lt1) of a series of distal-most contact points (Pt1) for the replacement tibial component (2) as a predetermined curve (15) on a first spherical surface (Sc1), said first spherical surface (Sc1) having its centre at the origin (0) and a radius (Rc1) in a range of (Rc1)=0.65 w+/−0.25 w, wherein (w) is the width of the knee prosthesis;
• (iii) at a given flexion angle γ for each contact point (Pt1) on the replacement tibial component (2), there exists a trace-line (Lt2) of a series of common distal-most contact points (Pt2) for a second spherical surface (Sc2) on the replacement femoral component (3), said second spherical surface (Sc2) identical to said first spherical surface (Sc1), said second spherical surface (Sc2) having its origin at origin (0) and a radius (Rc2=Rc1) whereby at a given flexion angle γ there exists a plane (E1) through origin (0) and a common contact point (Pt1/Pt2) with a guiding curve (Bi, Be) on the replacement tibial component (2) and a complementary guiding curve on the replacement femoral component (3), wherein both guiding curves (Bi, Be) are in a geometrically fixed relation to the common contact point (Pt1/Pt2) for the given flexion angle γ;
• and
• (iv) a shape of guiding curves (Bi) and (Be) is progressively changed by each change of flexion angle γ to generate an enforced gliding movement and an enforced rolling movement in a flexion direction and in an extension direction.