Diagnostic accuracy of candidate MRI knee osteoarthritis definitions versus radiograph in an acute anterior cruciate ligament injury cohort

We tested diagnostic accuracy of previously proposed magnetic resonance imaging (MRI) OA definitions in a cohort following acute anterior cruciate ligament (ACL) injury.We studied participants with posteroanterior and lateral knee radiographs and MRIs 5 years after ACL injury, scored using the Anterior Cruciate Ligament Osteoarthritis Score. Radiographic OA (ROA) was defined using Osteoarthritis Research Society International scoring of osteophytes and joint space narrowing considering medial/lateral tibiofemoral and patellofemoral compartments. We tested three candidate MRI OA definitions that performed well in an older adult cohort. "MOST simple" required cartilage score ≥2 (range 0-6) and osteophyte score ≥2 (0-7); "MOST optional" included cartilage score ≥2 and osteophyte score ≥2, and either bone marrow lesions (BML) ≥1 (0-3) or synovitis ≥2 (0-3). The third, a Delphi panel definition, included nonzero scores for cartilage, osteophyte, BML, meniscus and other structures. We calculated sensitivity and specificity with 95% confidence intervals for each MRI definition versus ROA.We included 113 participants (mean age 26 years, 26% female). At 5 years, 29 (26%) had ROA. "MOST simple" had a sensitivity of 52% (95% CI 33-71%), and specificity of 76% (95% CI 66-85%). Sensitivity and specificities for "MOST optional" were 28% (95% CI 29-67%) and 83% (95% CI 74-91%), respectively. The Delphi panel definition had a sensitivity of 48% (95% CI 29-67%) and specificity of 77% (95% CI 67-86%).Simple MRI-based OA definitions requiring at least cartilage damage and an osteophyte have low sensitivity and high specificity in young persons after knee injury. This article is protected by copyright. All rights reserved.