An anterior cruciate ligament (ACL) rupture is a very common musculoskeletal injury. The number of ACL reconstructions is increasing, both in the Netherlands and worldwide. Substantial progress has been made in surgical technique: from open to arthroscopic procedures. An ACL reconstruction will not diminish the chance of osteoarthritis, and the biomechanical properties of the knee will never be the same as before the trauma. An ACL reconstruction does, however, reduce the chance of instability, or 'giving way', which is the most important indication for surgical intervention. There are insufficient long-term results described in the literature to indicate either surgery or conservative measures as the treatment of choice. Treatment should be individually determined, taking into consideration factors such as: pattern of symptoms, degree of instability, desire to practise sport, age and willingness to commit to a 9-month rehabilitation programme.