Background: We are not aware of any previous studies in which independent measurements of function with validated outcome questionnaires such as the Knee Injury and Osteoarthritis Outcome Score and the International Knee Documentation Committee score were evaluated five years after reconstruction of the anterior cruciate ligament. We hypothesized that patient demographics, mechanism of injury, and intra-articular injuries and their treatment are factors associated with function five years after reconstruction of the anterior cruciate ligament. Methods: A consecutive series of unilateral, arthroscopically assisted primary reconstructions of the anterior cruciate ligament performed by one surgeon using a patellar tendon graft was evaluated. Data on patient demographics, injury variables, and intra-articular lesions noted at the time of surgery were collected prospectively. Multivariable regression analysis was used to identify independent predictors of outcomes as measured with five questionnaires. Results: Sixty-nine percent (217) of 314 knees with a reconstruction of the anterior cruciate ligament were followed for an average of 5.4 years. The average age at the time of the operation was twenty-seven years. Independent predictors of a worse outcome, which was measured with the overall Knee Injury and Osteoarthritis Outcome Score, the International Knee Documentation Committee score, the Lysholm score, and the Western Ontario and McMaster Universities Osteoarthritis Index score, included the patient's recollection of hearing or feeling a pop at the time of the injury, a weight gain of >15 lb (6.8 kg), and no change in educational level since the surgery. There was a lack of association between the outcome and either the occurrence or the form of treatment of a meniscal tear or chondromalacia of the articular cartilage. Conclusions: To our knowledge, we performed the first prospective cohort study to evaluate the prognosis following reconstruction of the anterior cruciate ligament by identifying significant associations between multiple variables and clinical outcomes as measured with validated questionnaires. The clinician can counsel patients about the intermediate-term functional outcomes of reconstructions of the anterior cruciate ligament on the basis of these findings. Suggestions regarding weight control and future education may improve intermediate-term outcomes. Level of Evidence: Prognostic Level II.