Association of physical examination knee effusion with bone marrow lesions: cross-sectional and longitudinal analyses of a population-based cohort.

OBJECTIVE: To determine the association of physical examination (PE) effusion with prevalence of bone marrow lesions (BML) on MRI, and incidence/progression of BML over 3 years in knee osteoarthritis (OA).

METHODS: A population-based cohort with knee pain (N=255) was assessed for PE effusion. On MRI, BML was graded 0-3 (none, mild, moderate, severe), incidence/progression defined as a worsening in the sum of BML scores over six surfaces by ≥1 grade. We analyzed the full cohort and mild disease subsample with Kellgren-Lawrence (KL) grade <3. Cross-sectional logistic and longitudinal exponential regression analyses were performed, adjusted for age, sex, BMI and pain. We calculated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for PE effusion vs. BML (prevalence and incidence/progression).

RESULTS: Weighted mean age was 56.7 years, mean BMI 26.5, 56.3% were female, 20.1% had PE effusion and 80.7% had KL<3. PE effusion was significantly associated with prevalent BML in the full cohort (OR 6.10; 95% CI 2.77, 13.44) and KL<3 cohort (OR 6.88, 95% CI 2.76, 17.15). Sensitivity/specificity/PPV/NPV were respectively 34.6/92.5/79.9/62.1% and 31.7/94.0/75.5/70.1%. Longitudinally, PE effusion was not significantly associated with BML incidence/progression in the full cohort (HR 1.83, 95% CI 0.95, 3.52) or KL<3 cohort (HR 1.73, 95% CI 0.69, 4.33). Sensitivity/specificity/PPV/NPV were respectively 32.0/82.2/42.2/74.9% and 21.2/85.6/30.1/78.8%.

CONCLUSION: BMLs on MRI can be predicted from PE effusion cross-sectionally with high PPV of 79.9%. Assessment for knee effusion on physical examination is useful for determining potential candidates with BML before costly MRI screening for recruitment into clinical trials. This article is protected by copyright. All rights reserved.