Inclusion Criteria:  Acute ACL injury (< 4 weeks) before surgical treatment Patient given written consent to participate in the study, Patient able to understand the protocol and willing to comply with its rules. Social security affiliated  Exclusion Criteria:  Age < 18 years ou > 45 years, ACL rupture associated with fracture or complex meniscal tear or lesion to the lateral collateral ligament or posterior cruciate ligament History of ligament surgery on the affected and non-affected knee. fracture Isokinetic contraindications : cardiorespiratory, metabolic, neurological, cancer or hematological pathology contraindicating physical activity, long term steroid use (> 3 months), pregnancy, skin problems under load cell, osteoporosis, anticoagulants Patient under the protection of adults Informed consent not obtained