This attachment device (2) comprises a support element (3) intended to provide support against the external cortex of a bone and provided with a passage opening (7), and a flexible connection element (8) configured for connecting the ligament transplant to the support element. The connection element (8) comprises a tubular portion (9) configured to extend through the passage opening (7) and able to be deformed between a first state in which the tubular portion (9) has a first internal diameter, and a second state in which the tubular portion (9) has a second internal diameter less than the first internal diameter. The connection element(8) also comprises a first and a second traction portion (11, 12) respectively arranged on each side of the tubular portion (9), the tubular portion (9) being configured to be deformed into its second state when traction is exerted on at least one of the first and second traction portions (11, 12).
