Combined effect of underwater ultrasound and custom-made insoles in rheumatoid arthritis: a randomized controlled trial

BACKGROUND: To investigate the effects of underwater ultrasound therapy alone and in combination with custom-made insoles in individuals with rheumatoid arthritis (RA). METHODS: This single-blind, randomized controlled trial included 75 patients with mild-to-moderate RA and foot pain, who were randomly allocated into three groups: control group (CG), underwater ultrasound group (UG), and underwater ultrasound plus custom-made foot insole group (IG). Interventions were applied over a 6-week period. Outcome measures included the Health Assessment Questionnaire (HAQ), Manchester-Oxford Foot Questionnaire (MOFQ), Timed Up and Go test (TUG), Berg Balance Scale (BBS), Static Plantar Pressure Distribution (SPPD), Single Heel-Rise Test (SHRT), and ankle circumference (AC). Assessments were performed before and after the intervention period. RESULTS: = 0.209) and selected SPPD parameters (RF, RB, and LB; p < 0.05), suggesting differential changes over time between groups. No significant group × time interactions were observed for MOFQ, TUG, BBS, SHRT, or AC, indicating comparable clinical improvements among groups. In contrast, SPPD demonstrated significant between-group differences, particularly in the group receiving custom-made foot insoles (p < 0.05). CONCLUSION: Underwater ultrasound therapy was associated with overall improvements in functional status, mobility, balance, and muscle performance in patients with rheumatoid arthritis. While clinical outcomes improved similarly across groups, the addition of custom-made insole mainly enhanced plantar pressure distribution, indicating a primary biomechanical benefit. TRIAL REGISTRATION: The study was registered on the Clinical Trials Registry (registration number: NCT06753552). Key Points • A six-week underwater ultrasound intervention resulted in significant improvements in functional status, mobility, balance, and plantar flexor muscle endurance in individuals with rheumatoid arthritis, regardless of treatment group. • The addition of custom-made foot insoles did not lead to superior clinical outcomes but provided distinct biomechanical advantages by significantly modifying Static Plantar Pressure Distribution. • Group-specific differences were primarily observed in plantar pressure parameters, indicating that insoles mainly influence biomechanical load redistribution rather than subjective clinical outcomes. • Underwater ultrasound may serve as a supportive therapeutic modality in rheumatoid arthritis, while the integration of custom-made foot insoles may offer additional biomechanical benefits, particularly in patients with foot involvement.