Reduced forearm muscle thickness and hand strength in patients with rheumatoid arthritis: an ultrasonographic cross-sectional study

The aim of this study was to compare forearm muscle thickness measured ultrasonographically in patients with rheumatoid arthritis (RA) with that of a healthy population and to investigate the relationship between this thickness and clinical, sociodemographic, and laboratory data in the patient group. This cross-sectional study included 140 participants: 70 RA patients and 70 healthy controls. Forearm muscle thickness was measured ultrasonographically from the anterior forearm in radial and ulnar regions, and hand grip strength was assessed with a dynamometer. Pain was evaluated using the Visual Analog Scale (VAS), functional status with the Health Assessment Questionnaire (HAQ), hand function with the Duruoz Hand Index (DHI), and disease activity with the Disease Activity Score-28 (DAS28). Results: There were no significant differences in sociodemographic data between the groups (p > 0.05). Ulnar muscle thickness was significantly lower in the RA group than in the control group (3.13 ± 0.37 vs. 3.55 ± 0.33 cm) (p < 0.05). Radial muscle thickness was also reduced in RA patients compared to controls (1.69 ± 0.24 vs. 1.94 ± 0.30 cm) (p < 0.05). Hand grip strength was 20.66 ± 7.78 kg in RA patients and 27.06 ± 9.59 kg in controls. Both measures were negatively correlated with disease duration, HAQ, and DHI (p < 0.05). DAS28 showed a negative correlation with ulnar muscle thickness and handgrip strength (p < 0.05), but not with radial muscle thickness (p > 0.05). These findings demonstrate that forearm muscle thickness is reduced in RA patients and is strongly associated with handgrip strength, disease activity, and functional status. Since decreased muscle mass contributes to loss of hand strength and functional impairment, forearm muscle thickness may represent a valuable parameter for clinicians to consider in the assessment and follow-up of RA patients.