Prevalence of Early Knee Osteoarthritis Illness Among Various Patient-Reported Classification Criteria After Anterior Cruciate Ligament Reconstruction.

OBJECTIVE To compare the prevalence of participants meeting different patient-reported criteria for early osteoarthritis (OA) illness after anterior cruciate ligament reconstruction (ACLR). METHODS Participants completed the Knee Injury and Osteoarthritis Outcomes Score (KOOS) at a single time-point at 5.0-7.9 months post-ACLR. We used established KOOS subscale criteria (i.e., Luyten_Original and Englund_Original) to define patient-reported early OA illness. A two-by-two contingency table and McNemar's test were used to compare the prevalence of participants that met the Luyten_Original versus Englund_Original KOOS criteria for early OA illness. These analyses were repeated using KOOS subscale thresholds based on established population-specific patient acceptable symptom state (PASS) within the Luyten and Englund KOOS criteria (i.e., Luyten_PASS and Englund_PASS). RESULTS A greater prevalence of participants with ACLR met the Luyten_Original criteria (n=165, 54%) compared to those who met the Englund_Original criteria (n=128, 42%; χ2 =19.3, p<0.001). When using the KOOS subscale PASS as thresholds, a significantly greater prevalence of participants with ACLR met the Luyten_PASS criteria (n=133, 43%) compared to those who met the Englund_PASS criteria (n=85, 28%; χ2 =48.0, p<0.001). When combining the Luyten and Englund KOOS criteria and using the original/PASS subscale thresholds, respectively, 40/57% of participants met neither, 24/15% met only one, and 36/28% met both KOOS criteria. CONCLUSION Regardless of the classification criteria used to define early OA illness, it is concerning that 28-54% of patients report considerable symptoms at ~6 months post-ACLR. Our findings will improve the classification criteria to define early OA illness, which may raise awareness for the need of population-specific criteria. This article is protected by copyright. All rights reserved.