A customised patient-specific 4-in-1 femoral finishing cutting jig comprising a cutting block which is configured to be placed, in use, in contact with the distal resection surface (sd) of a femur (f); the jig comprising reference means (R; 9; 10) which are configured to position, in use, said block relative to the distal resection surface (sd) in a predetermined and patient-specific manner; wherein the block has the shape of a rectangular parallelepiped having a proximal surface configured to be placed in contact, in use, against the distal resection surface (sd) of the femur (f), a distal surface opposite the proximal surface, an anterior surface, a posterior surface, a lateral surface and a medial surface, the proximal surface and the distal surface are the surfaces with greatest extension of the block, the anterior surface is configured to be positioned, in use, in the vicinity of the anterior part of the femur (f), the posterior surface is opposite the anterior surface, the lateral surface and medial surface are opposite each other and are perpendicular to the anterior, proximal, posterior and distal surfaces; wherein the block has distributed along a first axis (Y') parallel to the antero-posterior axis of the femur (f): an anterior guide having a first guide surface which is configured to guide, in use, a cutting instrument during performance of an anterior resection (ra), the anterior guide extending through the entire cutting block and establishing communication between the proximal surface and the distal surface of the block; an anterior slot having a second guide surface which is configured to guide, in use, a cutting instrument during performance of an anterior chamfer cut (sa), the anterior slot extending through the entire cutting block and establishing communication between the proximal surface and the distal surface of the block; a posterior slot having a third guide surface which is configured to guide, in use, a cutting instrument during performance of a posterior chamfer cut (sp), the posterior slot extending through the entire block and establishing communication with the proximal surface and the distal surface of the block; and a posterior guide having a fourth guide surface which is configured to guide, in use, a cutting instrument during performance of a posterior resection (rp), the posterior guide extending through the entire block and establishing communication between the proximal surface and the distal surface of the block; characterized in that the reference means (R; 9; 10) comprise a first contact element (9; 10) having a first surface (11; 12) which is configured to face, in use, a first femoral condyle (cfl; cfm) and is customised and patient-specific; said first surface (11; 12) being configured to be placed against a respective portion of a first femoral condyle (cfl; cfm) having a corresponding profile; the reference means (R; 9; 10) comprising a second contact element (10; 9) having a second surface (12; 11) which is configured to face, in use, a second femoral condyle (cfm; cfl) and being customised and patient-specific; said second surface (12; 11) being configured to be placed against a respective portion of a second femoral condyle (cfm; cfl) having a corresponding profile; said first contact element and said second contact element projecting at the rear from the posterior surface of the block and being configured to extend, in use, at least partially along the femur (f).