Femoral stem attachment for a modular knee prosthesis

A modular knee prosthesis includes a femoral component having a pair of laterally spaced apart condylar portions each having a superior, articulation surface and an inferior surface. A boss structure is disposed between and connects the condylar portions. The boss structure has an inferior surface that extends generally horizontally in the transverse plane, and an opposed superior surface. The boss structure has an aperture having a selected configuration formed therein and which extends between the inferior and superior surfaces. The boss structure has formed on the superior surface thereof a positioning structure, e.g., a plurality of grooves, that define one or more positions, in the transverse plane, in which to seat a femoral stem assembly. A washer is mountable upon the superior surface of the boss structure and over a portion of the boss aperture. The washer includes at least one detent that cooperates with the positioning structure to secure the washer in one of the mounting positions.