A modular joint prosthesis system includes an articulation member, such as a cruciate retaining femoral component of a knee joint prosthesis, having a superior bone engaging surface, an inferior articulation surface and one or more fixation pegs extending from the superior surface. An augmentation block mounts on the superior surface of the articulation member and has an aperture surrounding a respective fixation peg. The system further includes a compression collet seated between the aperture of the augmentation block and the fixation peg. In assembly, a securement device mounted over the fixation peg compresses the compression collet so as to engage the fixation peg and maintain the augmentation block on the articulation member.