Ultrasonographic features of tibialis posterior tendon in rheumatoid arthritis patients with pes planovalgus

The aim of this study was to assess the relationship between ultrasonographic features of tibialis posterior (TP) tendon in rheumatoid arthritis (RA) patients and associated pes planovalgus (PPV) foot deformity. Patients and methods This study included 20 (40 feet) RA patients with PPV and ultrasound-proven TP tenosynovitis. The following variables were recorded for patients: the number of tender and swollen foot joints count, foot posture index (FPI), Health Assessment Questionnaire, and Disease Activity Score 28 (DAS28). FPI is a clinical tool used to quantify the degree to which a foot is pronated, neutral, or supinated using the set criteria. Patients underwent high-resolution ultrasound of the TP tendon. Measurement of tendon diameter was recorded in the retromalleolar region. The presence of fluid around the TP tendon and levels of power Doppler signal (PDS) were assessed. Results High disease activity was detected in patients (mean DAS28 of 5.89). Eighteen (45%) feet had thickened transverse diameter and 15 (37.5%) feet had thickened longitudinal diameter. Twenty-three feet showed PDS. Nineteen feet had fluid around the tendon, detected only in the retromalleolar region. Regarding FPI, 14 feet were mild to moderate pronated feet and 26 feet were highly pronated feet. There were direct correlation between FPI and both DAS28 (p=0.05) and transverse diameter thickness (p=0.01). Highly pronated feet had higher DAS28 (p=0.03), increased transverse diameter thickness (p=0.04), more detection of fluid around the TP tendon (p=0.005) as well as higher incidence of PDS around the TP tendon (p=0.002). Conclusion Higher degree of pronation in RA feet with PPV is associated with ultrasonographic increased tendon thickness, PDS, and fluid around TP tendon. Early diagnosis and intervention for TP tenosynovitis may prevent progressive PPV foot deformity.