Currently, most patients with an anterior cruciate ligament injury undergo surgery. There is a general belief that surgical reconstruction is necessary to safely return to sports and to prevent early knee osteoarthritis or additional meniscus injuries. But there is insufficient scientific evidence to support this belief. Moreover, several studies show that surgical reconstruction of the cruciate ligament does not guarantee successful return to sports or the prevention of osteoarthritis and secondary meniscus injuries. Therefore, immediate surgery after an anterior cruciate ligament injury is questioned. So far, only two RCTs (KANON study and COMPARE study) have assessed this, and they could not show that immediate reconstruction is an added value (in terms of symptoms, knee function, activity level, osteoarthritis or additional meniscal injuries) compared to a conservative approach consisting of rehabilitation and late surgery for persistent knee instability. Therefore, this additional multicenter RCT, aims to 1) verify these results and 2) to identify predictors that predict which patients in the conservative group will not require late surgery. This has not been investigated to date. It is suspected that factors such as symptoms, strength, findings on the MRI scan and psychological factors may play a role in whether or not a patient will be able to successfully rehabilitate without surgical repair. This information is invaluable to physicians because it allows them to decide which treatment is best for the patient.