Anterior cruciate ligament (ACL) rupture is a common sports injury that affects the biomechanics of the knee joint. The optimal treatment of this injury is not only related to the clinical examination and objective findings, but also closely related to the patient`s activity level and expectations. So, it is very hard to determine an evidence-based, fixed clinical treatment guide or algorithm for clinicians. For the decision of conservative or surgical treatment of injury; multiple factors like partial or total rupture of ligament, injury time, patient`s age, additional intraarticular injuries, patient`s activity level and functional expectations, the degeneration level of joint should be considered. For middle-aged or old patients who has a sedentary life style, can be managed and followed conservatively with rehabilitation and neuromuscular training. However, patients with symptomatic instability who had an active life style or high demanding functional expectations, should be treated surgically in order to restore the normal knee biomechanics. The timing of surgery should be determined by consideration of additional injuries like meniscal or other ligaments, patient`s sportive activity level and expectations. Generally, a safe surgical treatment after ACL injury, should be performed after acute painful period of injury is ceased and knee range of motion with quadriceps muscle control is obtained. However, due to the delayed surgery and the risk of additional further injuries as a consequence of recurrent instability, the surgical treatment is recommended in the first 5 months of injury.