Study design: A descriptive and prospective prognostic cohort study, with consecutive recruitment of patients during a 12 month period from seven sites in Sweden Start of recruiting participants is October 2016. Most participants will receive a diagnosis from an orthopedic doctor approximately 2-4 weeks after their knee injury, and undergo rehabilitation for at least the first three months, before a decision regarding ACL reconstruction is taken (in line with current treatment guidelines). The patient cohort will be naturally divided into reconstruction plus rehabilitation, and rehabilitation only. Being included in the study will not affect the choice of treatment.