A fastening device for a tendon or ligament comprises a first device portion (2) suitable for being fastened to a bone of a person, a second device portion (3) provided with an engagement appendage (4; 4') for maintaining the tension of the tendon or ligament to be fastened and stably coupled to the first device portion (2), the second portion (3) being freely rotatable with respect to the first portion (2) in order to allow free relative rotation between the first (2) and the second (3) portion about a longitudinal axis (X) of the device (1), and fixing means (6, 11, 9e) which can be associated with the fastening device (1; 100) in order to fix the first (2) and the second (3) device portion to each other for rotation with respect to the longitudinal axis (X).
