The change in a validated knee measure score will be used as a performance measure for surgeons performing ACL reconstruction. Two measures will be created and reported by each surgeon. Surgeons will report the average knee measure change score for patients treated during the observation period. In addition, surgeons will produce a risk-adjusted knee measure change score ratio by dividing the average patient knee measure change score by the average predicted patient knee measure change score calculated using the formula provided. These measures will serve as sports medicine performance measures at the eligible surgeon level. Eligible validated knee patient reported outcome measures include: International Knee Documental Committee (IKDC) Subjective Knee Form (Pedi-IKDC), Knee Injury and Osteoarthritis Outcome Score (KOOS), Single Assessment Numeric Evaluation (SANE) [1]. Defining the population: CPT-4 procedure codes will be used to identify patients who received ACL reconstruction without treatment of chondral injury. ACL reconstruction during the reporting period CPT-4 Codes: 29888. Surgeons who performed a minimum of 25 ACL reconstructions a year will be eligible to submit this measure. Time period for data collection and reporting: This measure will be calculated using all patients who underwent ACL reconstruction during the observation period. Patients receiving ACL reconstruction during the period 18 to 6 months prior to the reporting data will be included in the analysis to ensure 6 months of patient-reported follow-up in the knee measure score are available. Measures: Two surgeon-level performance measures will be reported. The unadjusted measure will be the average 6-month knee measure change score across all ACL reconstruction patients treated by the surgeon. The adjusted measure will be the ratio of the average knee measure change score divided by the average predicted knee measure change score for all patients treated by the surgeon. Unadjusted measure: Average Knee Measure Change Score. NUMERATOR: Sum of knee measure change scores from pre-surgery to 6-months post-surgery across all ACL reconstruction patients in the denominator. DENOMINATOR: The number of all patients who received ACL reconstruction during the observation window from the surgeon. Type of score: Validated knee measure change score average. Risk adjusted measure: Knee Measure Change Score Ratio. NUMERATOR: Average 6-month knee measure change score for all ACL reconstruction patients treated by surgeon. DENOMINATOR: Average predicted 6-month knee measure change score for all ACL reconstruction patients treated by surgeon. Risk adjustment methods and variables: The predicted 6 month knee measure change scores are estimated for each patient using the Center for Effectiveness Research in Orthopaedics’ (CERortho) risk adjustment regression model that includes the following patient variables: age, gender, BMI, smoking status, comorbidities, worker’s compensation status, history or prior knee surgery, sport participation/activity level, osteoarthritis, concomitant chondral injury, the baseline knee measure, and baseline measures of pain, knee function, and quality of life.[2-4]. Variables included in the current CERortho risk model are based on information in available databases. CERortho plans to constantly update these specified variables based on input from evaluated surgeons and specialty organizations. Appendix A contains the list of baseline concepts from peer-reviewed literature that are thought to affect outcomes of treatment and will be candidates for future inclusion in the model. Type of score: Ratio score; Interpretation of score: Surgeons with ratio scores equal to 1 have quality scores equal to the average surgeon given the characteristics of their patients. Surgeons with ratio scores greater than 1 had knee change scores higher than average. Surgeons with ratios scores less than 1 had knee change scores lower than average given the characteristics of their patients. Definitions: Patient’s Knee Measure Score: A knee measure score is produced when the patient answers a validated knee assessment administered in the clinic or through an online portal. Patient’s Knee Measure Change Score: A patient’s change score is calculated by subtracting the patient’s knee measure score at baseline from the patient’s knee measure score at 6 months. Patient’s Knee Measure Predicted Adjusted Change Score: Knee measure change scores for patients are risk adjusted using a regression model that includes the following independent variables: age, gender, BMI, smoking status, comorbidities, worker’s compensation status, history or prior knee surgery, sport participation/activity level, osteoarthritis, concomitant chondral injury, the baseline knee measure, and baseline measures of pain, knee function, and quality of life.[2-4] The patient’s predicted knee measure change score is the dependent variable. The regression model produces a risk-adjusted predicted knee measure change score for each patient. Risk-adjusted Knee Measure Change Score Ratio: The ratio between the actual change scores and the predicted change scores (after risk adjustment) is the ratio score. The risk-adjusted knee measure change score represents risk-adjusted change corrected for patient characteristics. A risk-adjusted ratio score of one or greater should be interpreted as change scores that were as good as or better than predicted given the risk-adjustment variables of the patient. Risk-adjusted ratio change scores less than one should be interpreted as knee measure change scores that were less than predicted given the risk-adjustment variables of the patient. The surgeon ratio scores can be used to make comparisons across surgeons. Steps: 1. Prior to ACL reconstruction surgery the patient completes a baseline validated knee measure assessment which generates the patient’s knee measure score at baseline; 2. Six months after surgery, the patient completes the same validated knee measure assessment again, which generates the patient’s knee measure score at 6 months; 3. The patient’s raw, unadjusted knee measure change score is generated by subtracting the baseline score from the 6-month score; Unadjusted measure: 4. Patients’ knee measure change scores are averaged by surgeon. Adjusted measure:  5. A risk-adjusted knee measure change score is predicted using the CERortho risk-adjustment regression model. 6. Patients’ unadjusted and adjusted knee measure change scores are averaged by surgeon. 7. A risk-adjusted Knee Measure Change Score Ratio is generated for each surgeon. 8.The ratio scores for all surgeons in the database are ranked. See attached for references...