Cut-Off Values to Interpret Short-Term Treatment Outcomes After Arthroscopic Meniscal Surgery Measured With the Knee Injury and Osteoarthritis Outcome Score

OBJECTIVE: To determine the proportions of patients who (1) perceived their symptoms to be satisfactory, (2) perceived their treatment to have failed, or (3) perceived that they improved to an important degree at 3 months after arthroscopic meniscal surgery; and to determine Knee injury and Osteoarthritis Outcome Score (KOOS) subscale scores corresponding to the Patient Acceptable Symptom State (PASS), treatment failure, and the minimal important change (MIC) for improvement. DESIGN: Prospective cohort study. METHODS: Patients from the Knee Arthroscopy Cohort Southern Denmark who had arthroscopic meniscal surgery were included. The PASS, treatment failure, and MIC improvement values were calculated for the KOOS subscales with anchor-based approaches, using the adjusted predictive modeling method. Subgroup analyses were performed by stratifying by age (40 years or younger versus older than 40 years) and surgery type. RESULTS: Six hundred fourteen patients (44% female; mean ± SD age, 50 ± 13 years) were included. At 3 months after arthroscopic meniscal surgery, 45% of patients perceived their symptoms to be satisfactory, 19% perceived the treatment to have failed, and 44% to 60% perceived that they had improved to an important degree across the 5 KOOS subscales (for PASS/treatment failure, respectively: pain, 74 and 60 points; symptoms, 72 and 61 points; function in activities of daily living, 81 and 68 points; sport and recreational function, 43 and 26 points; and knee-related quality of life, 52 and 40 points; for MIC improvement: pain, 12 points; symptoms, 8 points; function in activities of daily living, 12 points; sport and recreational function, 17 points; and knee-related quality of life, 9 points). The PASS values were 6 to 17 points higher for patients 40 years or younger compared to patients older than 40 years. CONCLUSION: At 3 months after meniscal surgery, approximately half of the patients perceived their symptoms to have improved to an important degree, 4 in every 10 patients perceived their symptoms to be satisfactory, and 2 in every 10 patients perceived the treatment to have failed.