Method for constructing a digital model of a set of osseous joints, each osseous joint including two bones connected by a joint, of a given patient, assisted by a computer and wherein: - the computer includes at least one reference three-dimensional digital model of the set of osseous joints, said reference model being represented, at least in part, by rigid bodies modelling the bones and connected by joints in a reference position; - the geometry of said digital model, corresponding to the relative spatial position of each of the rigid bodies, is customised by specific geometric data derived directly or indirectly from medical images of the patient in said reference position; - said digital model is customised mechanically by modifications of interaction, mobility or rigidity parameters, of each of the joints connecting the rigid bodies according to characteristics observed on the patient; the mechanical customisation of the digital model consisting of: - acquiring the spatial positions of a portion of the rigid bodies and subsequently determining the positions of the other rigid bodies by interpolation, so as to obtain the relative positions of each of the rigid bodies of the digital model; - measuring relative positions corresponding to a general equilibrium position of the patient different from the reference position and resulting from the application of at least one determined strain on said patient; - computing, for each pair of rigid bodies, analytical functions for approximating the interaction parameters, and which applied to the digital model from the reference position lead to measured relative positions corresponding to the resultant equilibrium position from the application of the at least one strain on the patient. - the computer includes at least one reference three-dimensional digital model of the set of osseous joints, said reference model being represented, at least in part, by rigid bodies modelling the bones and connected by joints in a reference position; - the geometry of said digital model, corresponding to the relative spatial position of each of the rigid bodies, is customised by specific geometric data derived directly or indirectly from medical images of the patient in said reference position; - said digital model is customised mechanically by modifications of interaction, mobility or rigidity parameters, of each of the joints connecting the rigid bodies according to characteristics observed on the patient; - acquiring the spatial positions of a portion of the rigid bodies and subsequently determining the positions of the other rigid bodies by interpolation, so as to obtain the relative positions of each of the rigid bodies of the digital model; - measuring relative positions corresponding to a general equilibrium position of the patient different from the reference position and resulting from the application of at least one determined strain on said patient; - computing, for each pair of rigid bodies, analytical functions for approximating the interaction parameters, and which applied to the digital model from the reference position lead to measured relative positions corresponding to the resultant equilibrium position from the application of the at least one strain on the patient.