Methods and apparatus for planning and/or carrying out a total knee replacement surgical procedure on a knee of a leg of a patient are described. Anatomical data for the leg of the patient is obtained, which allows the femoral mechanical axis, the tibial mechanical axis and the joint line of the knee to be determined. A planned proximal tibial cut angle and a planned distal femoral cut angle are determined. A total knee replacement procedure is carried out on the knee of the patient, wherein a distal femoral cut is made using the planned distal femoral cut angle and a proximal tibial cut is made using the planned proximal tibial cut angle.