Minimal Clinically Important Difference and Patient Acceptable Symptom State for Patient-Reported Outcomes Following Common Arthroscopic Sports Surgeries of the Knee: A Systematic Review.

Background: Patient-reported outcome measures (PROMs) are widely used to capture patients' perspectives when evaluating outcomes after arthroscopic knee surgery. To aid in the interpretation of PROM scores at the individual level, the minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) are used. These metrics provide patient-centered thresholds for what constitutes a meaningful improvement and satisfactory state postoperatively. Purpose: To summarize available literature on MCID and PASS values for all PROMs across common primary arthroscopic knee sports surgeries. Study Design: Systematic review; Level of evidence, 4. Methods: MEDLINE, Embase, and Cochrane databases were queried from inception through January 13, 2025, to identify studies that calculated MCID or PASS values of PROMs after primary knee arthroscopic surgeries of the anterior cruciate ligament (ACL), meniscus, or cartilage. Study characteristics, MCID and PASS thresholds, and threshold calculation methods were extracted. MCID and PASS thresholds were aggregated by PROM, surgical treatment, and calculation method and then summarized using a range. Results: In total, 59 studies met the inclusion criteria; 52 studies calculated MCID thresholds, with 15 studies using anchor-based methods and 39 studies using distribution-based methods. A total of 21 studies calculated PASS thresholds; 35 studies calculated thresholds for ACL procedures, 15 studies for meniscus procedures, and 8 studies for cartilage procedures. ACL reconstruction was the most reported procedure (n = 32 studies). Thresholds were calculated for 18 different PROMs, with the International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC) being the most frequently reported instrument (n = 34 studies). The range of MCID thresholds for the IKDC after ACL reconstruction was 7.1 to 16.2 using anchor-based methods and 7.6 to 10.5 using distribution-based methods, while PASS thresholds ranged from 66.7 to 80.5. Conclusion: The heterogeneity observed in reported MCID and PASS values suggests that these metrics should be viewed as context-specific. While most studies in this review used distribution-based calculations to derive MCID values, anchor-based calculations should be prioritized in future studies as they better reflect the patient's perception of improvement. Overall, this study will allow investigators to use appropriate clinically relevant thresholds for designing randomized controlled trials, comparing the proportion of patients achieving a meaningful improvement and satisfactory state across different treatment arms, and establishing patient expectations for recovery.