The present invention relates to a computer assisted surgical navigation method for determining the patient-specific pressure that must be applied on one or both sides of a joint during the ligament balancing steps of an arthroplasty procedure, said method comprising:inserting a tensor (22) inside the joint between a first bone (8) and a second bone (2) when the joint is in a given angular orientationcontrolling the pressure applied by the tensor (22) to the joint so as to make it increase from a minimum value to a maximum valuemeasuring the evolution of the distance between the first and the second bones during said pressure increasedetermining the relationship between said distance and said pressureprocessing said relationship to determine said patient-specific pressure to apply to the joint.
