Inclusion Criteria:  men and women of legal age to be capable of discernment to have a telephone number or email address to communicate with the investigators, to have a device with internet access to access the mental imagery programs. to have had an ACL surgery performed by the Doctor Siegrist within the last three days using the Hamstrings Tendon Graft or the Kenneth Jones method.  Exclusion Criteria:  not having a good spoken knowledge of the French language recurrence of ACL injury in the same knee meniscal sutures associated fractures pre-existing balance problems (tested at recruitment) pre-existing neurological problems diagnosed by a doctor.