Progression of hindfoot valgus and its association with foot- and ankle-related quality of life in patients with rheumatoid arthritis: a retrospective study from KURAMA cohort

To clarify the impact of lower limb and hindfoot alignment and its changes on foot and ankle-related quality of life (QOL) over a 4-year period in patients with rheumatoid arthritis (RA). A total of 258 RA patients (516 feet) who underwent plain X-ray examination with hip-to-calcaneal (HC) view at baseline and a 4-year follow-up, along with Self-Administered Foot Evaluation Questionnaire (SAFE-Q) data at the follow-up were analyzed after excluding patients with prior lower limb surgery or severe ankle destruction (Larsen classification ≥ III or Takakura-Tanaka classification ≥ IIIa). Radiographic parameters representing lower limb and hindfoot alignment were measured using HC view, including hip-knee-ankle angle (HKA), tibio-calcaneal angle (TCA), talar tilt angle (TTA), and the changes of these angles. Clinical and laboratory factors collected included age, sex, BMI, autoantibody titer and positivity, methotrexate (MTX) use, biologic and targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) use, cumulative glucocorticoid dose, and Clinical Disease Activity Index. The primary outcome was the association between clinical and radiographic factors and ankle-related QOL. A generalized linear mixed model was used for statistical analysis. The mean age was 62.4 years, 87.2% were female, and 89.9% were seropositive. Over 4 years, hindfoot valgus (TCA) progressed from 4.3° to 6.0°. GLMM showed that age and cumulative glucocorticoid dose negatively affected QOL, while male sex, methotrexate dose, and b/tsDMARDs use were positively associated. Among radiographic parameters, valgus progression of TCA was significantly associated with poorer SAFE-Q outcomes in the "Shoe-related" and "General Health Perception" domains. Baseline HKA predicted valgus progression of TCA, whereas higher BMI, male sex, and larger baseline TCA predicted varus progression. Progressive hindfoot valgus deformity over 4 years, rather than static alignment, negatively impacts foot- and ankle-related QOL in RA patients, particularly in shoe-related function and general health perception. Baseline knee varus deformity predicts longitudinal hindfoot valgus progression.