Method and system for measuring the laxity of a joint of a human or an animal

The invention relates to a method of determining the laxity of a joint (9, 15) of a human (5) or an animal. The method comprises providing at least one patient-specific geometrical model (1) of at least one bone and/or at least one prosthesis comprised by the joint. Known loads are applied to the joint or to a part of the body connected to the joint, and a series of actual images (16) of the joint are obtained while the loads are applied. Then the at least one patient-specific geometrical model (1) is registered onto the actual images (16). Based thereon relative displacement and/or rotation of the at least one bone and/or at least one prosthesis is calculated as a function of the applied loads, and based thereon a measure of the laxity of the joint is determined. The invention further relates to a system for performing such a method and to a computer readable medium for performing such a method.