An orthopaedic instrument assembly comprises a customized patient-specific femoral cutting block having a customized patient-specific negative contour surface that is configured to receive a portion of a distal femur of a patient that has a corresponding contour, and a cutting guide. A ligament balancer is secured to the femoral cutting block and has a tibial base plate and a pair of femoral paddles, each of which can be moved relative to the tibial base plate.
