Background: Opioids provide effective pain relief for many adolescents following sports-injury surgery. However, a subgroup experiences poor pain relief with significant risk of developing iatrogenic problematic opioid use behaviors, such as persistent opioid use and opioid misuse (use in a way other than prescribed: e.g. longer duration, higher doses). Currently, our ability to predict this risk-benefit ratio for individual patients is limited by inadequate understanding of associated risk factors. Therefore, we aimed to 1) characterize opioid use over 14 days following surgery, 2) examine relationships between pre-operative risk factors (pain intensity, depressed mood, sleep disturbance, substance use history) and postoperative opioid use, and 3) determine rates of opioid misuse/persistent use at 2 months post-surgery. Hypothesis: We hypothesized finding 1) wide variability in opioid use over the first 14 days post-surgery, 2) higher pre-surgery pain intensity, depressed mood, sleep disturbance, and history of substance use associated with increased opioid use, and 3) 5-10% of patients reporting opioid use beyond 14 days from surgery. Methods: Prospective observational study of 50 adolescents (50% female) undergoing outpatient sports-injury (knee, shoulder, elbow) arthroscopic and limited-open surgery. Prior to surgery, participants were surveyed about pain symptoms, depressive symptoms, sleep disturbance, and a history of substance use using validated patient-reported questionnaires. All participants received opioids (oxycodone) to manage moderate-severe pain at home. Opioid use was objectively monitored using a novel medication adherence tracking device (electronic pill box). The primary outcome variable was the number of opioid doses used from the initial prescription following surgery. Generalized estimating equation (GEE) regression models examined associations between risk factor/predictor (pain, depression, sleep, substance use) and opioid use variables, controlling for time since surgery. Results: Mean age was 13 years (range 10-18 years). Mean opioid use was highly variable, ranging from 1-25 doses over the first 14 days following surgery (mean 8.5±5.8 doses). Pre-surgery pain (Beta(β)=0.39, p<0.0001), sleep disturbance (β =0.35, p=0.026), and history of substance use (β =0.22, p=0.04) predicted increased opioid use over 14 days. Surgery type and depressive symptoms were not associated with opioid use. At 2-month follow-up, 6/50 (12%) patients reported use of opioids beyond 14 days after surgery. Conclusion: Opioid use following sports-injury surgery varies widely and may be related to modifiable preoperative risk factors, suggesting an important role for screening and brief preoperative interventions. Up to 12% of patients used opioids up to 2 months following surgery, however, whether this phenomenon suggests opioid misuse versus persistent opioid use for pain remains unknown.