Background/Purpose: To investigate the construct validity of Outcome Measures in Rheumatology (OMERACT) ultrasound scores for knee osteoarthritis (OA) with pain, other symptoms, and OA severity on radiographs and magnetic resonance imaging (MRI) counterparts.

Methods: A subgroup of community-recruited participants with symptomatic and mild-moderate radiographic knee OA participating in a randomized controlled trial of platelet-rich plasma were included in this study. At baseline, participants underwent dynamic ultrasound assessment using Aplio Platinum 500 machine, Toshiba, with a multi-frequency linear transducer (6-18MHz) according to the OMERACT scanning protocol. Using the published ultrasound image atlas by OMERACT group, a physician operator obtained semi-quantitative scores for synovitis, cartilage thinning, osteophytes and medial meniscal extrusion, and a dichotomous score for power Doppler (PD) signals, effusion and synovial hypertrophy. Clinical outcomes included the severity of pain on an 11-point numerical rating scale and Knee Injury and Osteoarthritis Outcome Score (KOOS) symptoms and pain sub-scores. The Likert responses of KOOS ranged from “none” to “extreme”. and scores ranged from 0 to 100, with lower scores indicating worse symptoms.  OA severity was assessed using the Kellgren-Lawrence grade (KLG) on plain radiograph. MRI osteoarthritis knee score (MOAKS) was used on non-contrast-enhanced MRI sequences to evaluate cartilage loss (any or full thickness) from patellofemoral, medial and lateral tibiofemoral compartments, osteophytes from 12 different sites, medial meniscal extrusion, effusion-synovitis and Hoffa’s synovitis. Linear regression was used to determine the associations of ultrasound OA pathologies with pain and KOOS sub-scores adjusting for confounders such as age, gender, disease duration and KLG as appropriate, and Spearman’s correlation was used for the relationship with KLG and MOAKS.

Results: Eighty-nine participants (female, 53.9%; body mass index, mean= 27.5±6.4) were included in the analysis. Synovial hypertrophy, PD signals and meniscal extrusion scores were associated with increased pain severity (B = 0.92, 95% confidence interval CI 0.25, 1.58); B = 0.73(95% CI 0.11, 1.35) and B = 1.01(95% CI 0.22, 1.80) respectively (Figure 1A). All ultrasound scores, except for cartilage grade, demonstrated associations with KOOS symptoms (Figure 1B) while only PD signals and meniscal extrusion were associated with KOOS pain (Figure 1C). All ultrasound scores, except for PD signals, were significantly correlated with KLG (Figure 2). Most ultrasound pathologies revealed moderate to good correlation with their MRI counterparts with ultrasound synovitis having the greatest correlation [0.69(95% CI 0.60, 0.78)] (Figure 3).

Conclusion: OMERACT ultrasound scores revealed good construct validity against commonly used measurement tools such as pain, function, and radiographic and MRI features, providing evidence to support its use as a standardized tool for determining ultrasound OA phenotypes.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/construct-validity-of-omeract-ultrasound-knee-scores-with-pain-other-symptoms-radiographic-and-mri-findings/