In this retrospective research results of ACL reconstruction in adolescent will be evaluated. As we know ACL ruptures become more frequent and more often operated these days. According to literature the results in patients younger than 20 years old are worse. Therefore clinical and MRI evaluation will be performed. The aim of the study is to assess subjective and objective functional outcome of ACL reconstruction with follow-up at least 3 years. MRI scans will be evaluated to highlight any early signs of osteoarthritis and describe graft morphology. IKDC, KOOS scales will be utilised for subjective evaluation. Clinical tests such as Lachman's, pivot shift, Appley's along with anterior tibial shift measurement with digital arthrometer for objective assessment will be also performed. Additionally isokinetic tests will be performed in two speeds of 60 and 180 deg/s. Most of important isokinetic parameters such as peak torque, torque in 30 deg, time to peak torque, peak torque to body weight both for quadriceps and hamstrings will be measured . Preliminary group of patients consists of 150 cases with follow-up at least 3 years, operated in age 12-17 years. All cases available for the study will be assessed with methodology above. Dedicated statistical test will be utilised to evaluate the results.