An orthopaedic prosthesis assembly comprising: a tibial bearing configured to be coupled to a tibial tray, the tibial bearing having a platform and a spine extending upwardly from the platform, the spine having a posterior cam surface, the posterior cam surface including a concave cam surface and a convex cam surface and first and second femoral components (100; 200), each of the first and second femoral components being configured to couple separately with the tibial bearing to articulate with the tibial bearing, and including (i) a pair of spaced apart condyles (104, 106; 204, 206) defining an intercondylar notch (108; 208) between them and (ii) a posterior cam (110; 210) positioned in the intercondylar notch, the posterior cam including a posterior cam surface (114; 214), in which the posterior cam surface of the first femoral component includes a concave cam surface and a convex cam surface, the concave cam surface of the posterior cam being configured to contact the convex cam surface of the spine during a first range of flexion and the convex cam surface of the posterior cam being configured to contact the concave cam surface of the spine during a second range of flexion, and in which the posterior cam surface of the second femoral component is convex, characterised _in that the posterior cam surface of the second femoral component does not include a concave section so that, as flexion of the knee joint increases, contact between the posterior cam transitions from contact between the convex cam surface of the posterior cam and the convex cam surface of the spine to contact between the convex cam surface of the posterior cam and the concave surface of the spine. a tibial bearing configured to be coupled to a tibial tray, the tibial bearing having a platform and a spine extending upwardly from the platform, the spine having a posterior cam surface, the posterior cam surface including a concave cam surface and a convex cam surface and first and second femoral components (100; 200), each of the first and second femoral components being configured to couple separately with the tibial bearing to articulate with the tibial bearing, and including (i) a pair of spaced apart condyles (104, 106; 204, 206) defining an intercondylar notch (108; 208) between them and (ii) a posterior cam (110; 210) positioned in the intercondylar notch, the posterior cam including a posterior cam surface (114; 214), in which the posterior cam surface of the first femoral component includes a concave cam surface and a convex cam surface, the concave cam surface of the posterior cam being configured to contact the convex cam surface of the spine during a first range of flexion and the convex cam surface of the posterior cam being configured to contact the concave cam surface of the spine during a second range of flexion, and in which the posterior cam surface of the second femoral component is convex, characterised _in that the posterior cam surface of the second femoral component does not include a concave section so that, as flexion of the knee joint increases, contact between the posterior cam transitions from contact between the convex cam surface of the posterior cam and the convex cam surface of the spine to contact between the convex cam surface of the posterior cam and the concave surface of the spine.