A method of surgically preparing a distal end of a femur for implantation of a femoral prosthetic component includes positioning a base cutting block and an intramedullary adaptor on the distal end of the femur such that a first end of the intramedullary adaptor is received in the medullary canal of the femur and the intramedullary adaptor is secured to the base cutting block, attaching a first modular cutting block to an anterior side of the base cutting block, resecting a first portion of the distal end of the femur using a cutting guide defined in the first modular cutting block, the cutting guide of the first modular cutting block, and resecting a second portion of the distal end of the femur using a base cutting guide defined in the base cutting block.