Background/Purpose: Musculoskeletal ultrasound (MSUS) has been well known to aid in both early diagnosis and monitoring of inflammatory arthritis. Patients with an elevated BMI have an increased prevalence of inflammatory joint disease, pose a more challenging clinical exam, and traditional disease activity scores may overestimate tender joint counts1. This study aims to assess differences in reasons for referral to the rheumatology MSUS Clinic and in joint findings among patients with elevated BMI compared to those with a normal BMI.  

Methods: A retrospective analysis of 203 patients that attended the MSUS Clinic at Montefiore Medical Center, a tertiary academic center, was performed from March 2022 to September 2023. Electronic health record data was extracted to assess demographics, referral questions, joint findings, and underlying rheumatologic diseases. Differences in these domains between patients with normal BMI, overweight, and obese BMI were assessed with bivariate analyses using Pearson’s Chi-squared tests and Fischer’s exact test as appropriate. Patients were divided into three groups: normal weight (BMI 18.5-24.99), overweight (BMI 25-29.99), and obese (BMI ≥30).

Results: There were no significant differences seen in the reason for referral to the MSUS clinic between the three groups. Normal weight patients were referred more frequently for monitoring and evaluation of inflammatory joint disease, while patients with obesity were more frequently referred for procedures, however this was not statistically significant (figure 2). Patients with a normal BMI were significantly more likely to have active inflammatory arthritis on ultrasound (38% vs. 22% in overweight patients and 13% in obese patients p< 0.01) (figure 3). Joint findings between the groups were otherwise not statistically significant, however, there was a trend towards increased chronic inflammatory arthritis in patients with obesity (figure 3). 

Conclusion: MSUS has an important role in identifying inflammatory arthritis. Among our patient population, overweight and obese patients were less likely to have active inflammatory arthritis, which is concordant with previous research demonstrating patients with elevated BMI have less hyperemia on ultrasound1. However, in our cohort, there was a non-significant trend toward more chronic inflammatory arthritis. This differs from previous ultrasound studies showing less radiographic joint damage in patients with obesity based on the proposed theories of decreased bone remodeling in obesity and protective effects of adipocytes on the synovium1. These results highlight the need for more consistent MSUS in elevated BMI patients with inflammatory arthritis as the length to the initial diagnosis of inflammatory arthritis in this cohort may be contributing to this trend. Patients with elevated BMI were referred more often for procedural accuracy rather than evaluation and monitoring of inflammatory arthritis, which also highlights the need for more referrals for evaluation and monitoring in this cohort.1. Bauer EM, et al. Joint-specific assessment of swelling and power Doppler in obese rheumatoid arthritis patients. BMC Musculoskelet Disord. (2017)

Table 1. Patient Characteristics by BMI Category

Table 2. Referral Reasons to the MSUS Clinic by BMI Category

Table 3. MSUS Joint Findings by BMI Category

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/musculoskeletal-ultrasound-clinic-referral-patterns-and-joint-findings-in-a-tertiary-care-center-amongst-patients-with-elevated-bmi-and-inflammatory-arthritis/