Patient-reported foot dysfunction and quality of life in psoriasis: the independent association of psoriatic arthritis beyond skin disease severity.

OBJECTIVE

This study aimed to compare patient-reported foot-related pain, disability, and activity limitation, assessed using the Foot Function Index (FFI), and health-related quality of life, assessed using the Short Form-36 (SF-36), between participants with psoriasis and healthy controls, and to examine the independent associations of psoriatic arthritis (PsA), skin disease severity, cutaneous foot involvement, nail involvement, and body mass index (BMI) with these outcomes.

MATERIALS AND

METHODS

This cross-sectional study included 114 participants with psoriasis and 142 healthy controls. Between-group comparisons were performed using the Mann-Whitney U test, and BMI-stratified sensitivity analyses were conducted. Factors independently associated with total FFI were examined using multiple linear regression with variance inflation factor (VIF) assessment and 95% confidence intervals. Multiple testing correction was performed using the Benjamini-Hochberg method.

RESULTS

Participants with psoriasis had significantly higher FFI scores and lower SF-36 scores across all subscales than healthy controls (all FDR-adjusted p < 0.001; Cohen's d: 2.57-3.46). For total FFI, between-group differences persisted across BMI strata (d = 3.30-3.93; all p < 0.001). In multiple regression analysis, PsA showed the strongest independent association with total FFI score (β = 0.385, p < 0.001). BMI (β = 0.270, p = 0.003) and PASI (β = 0.217, p = 0.044) were also independently associated with total FFI (R2 = 0.302), whereas cutaneous foot involvement was not (p = 0.982).

CONCLUSION

People with psoriasis reported substantially greater foot-related pain, disability, and activity limitation and poorer health-related quality of life than healthy controls. PsA status showed the strongest independent association with worse FFI scores, while BMI and PASI were also associated. Because FFI is a patient-reported outcome, these findings reflect perceived foot-related burden rather than objective evidence of specific joint, entheseal, structural, or gait abnormalities. Key Points • Participants with psoriasis reported substantially greater foot-related pain, disability, and activity limitation and poorer health-related quality of life than healthy controls. • Psoriatic arthritis showed the strongest independent association with worse total FFI scores after adjustment for skin disease severity and other covariates. • Higher BMI and PASI were independently associated with worse patient-reported foot-related function. • FFI may provide complementary information on foot-related patient burden, but it should not be interpreted as an objective measure of specific musculoskeletal pathology.