Inclusion Criteria:  18 - 35-year-old men; a normal contralateral knee, not a longer period than 3 months after ACL rupture.  Exclusion Criteria:  Participants were excluded if either knee had previously been injured or had undergone surgery, if they had concurrent osteoarthritis, if they had injured the posterior cruciate ligament, lateral collateral ligament, or posterolateral complex of the knee, or if they had a grade III tear of the medial collateral ligament.