Aim of the study was to access how individual's motives for participation in sports impact on self-reported outcomes 2 years after an anterior cruciate ligament injury. Based on a longitudinal cohort study, this secondary analysis present data from the Knee Anterior Cruciate Ligament, Nonsurgical versus Surgical Treatment (KANON) study, a randomized controlled trial. At baseline, 121 patients recorded in an initial questionnaire that their motives for sports participation fell into four categories: achievement, health, social integration, or fun and well-being. These four categories were used as variables in the analyses. All 121 subjects completed the 2-year follow-up. The largest improvement was seen in the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscale sports and recreation function, with an effect size of 2.43. KOOS sports and recreation function was also the subscale score best predicted by the motives for sports participation. Baseline motives achievement and fun and well-being predicted worse levels of pain and function 2 years after the injury, even after adjusting for age, gender, treatment and baseline scores. Psychological aspects, such as motives for participation in sport, can be factors in predicting of patient-reported outcomes 2 years after injury. Evaluating motives for sports participation may help predict the outcome 2 years after ACL injury.