Anterior cruciate ligament (ACL) reconstruction is presently evolving rapidly. In order to monitor the developments in surgical methods and clinical outcome, a national clinical database for knee ligament reconstructions was established in 2005 in Denmark. This study presents the first data with 2 year follow-up from the Danish ACL registry. All orthopaedic departments performing ACL reconstructions in Denmark, including private clinics, report to the registry. The database includes both surgery- and patient-related data. The surgeon reports anamnestic, objective knee laxity and operative data including graft and implant choices. At 1 year control, complications, reoperations, and objective knee laxity are recorded. The patient registers the Knee injury and Osteoarthritis Outcome Score (KOOS) and Tegner function score preoperatively and at 1, 5 and 10 years follow-up. During the first 30 months, 5,872 knee-ligament reconstructions were registered. A total of 4,972 were primary ACL reconstructions, 443 were ACL revisions and 457 multiligament reconstructions. A total of 85% of all knee ligament reconstruction were reported to the database. A total of 71% of primary ACL reconstruction used hamstring tendon grafts and 21% used patella tendon graft. Meniscus injuries were treated in 35% of all patients. A total of 17% had significant cartilage lesions. At 2 years follow-up 3% of primary reconstructions were revised. Follow-up KOOS demonstrated specific differences between primary ACL, revision ACL, and multiligament reconstructions. Sports/recreation score were 40, 32, 28 and quality of life score were 40, 32, 33 for the respective groups. This study presents the first follow-up data from a national ACL registry. These data will become new international reference materials for outcome measures before and after ACL surgery. The database will enable future monitoring of ACL reconstruction techniques and outcome.