Functional Impact of Structural Damage in Psoriatic Arthritis: Insights from a Prospective Cohort Study

Abstract

Objective

To examine the association between radiographic structural damage and physical function (PF) in psoriatic arthritis (PsA).

Methods

Data were analyzed from a large longitudinal PsA cohort. PF was measured using the Health Assessment Questionnaire (HAQ, 0–3) and Short Form-36 PF subscale (SF-36, 0–100); radiographic joint damage was measured using the modified Steinbrocker score (mSS, 0–168). Associations between PF and mSS were analyzed using linear mixed models. We also evaluated the impact of the presence of any damaged joint (grade 2–4), joint damage by individual grades, and the number of damaged joints (grade 2–4) per patient on PF.

Results

Of 1,177 patients (mean ± SD age 44.61 ± 12.76 years; 55.8% men), baseline mSS was 2 (interquartile range [IQR] 0–8.5), HAQ was 0.62 (IQR 0.12–1.12), and SF-36 PF was 60 (IQR 35–85). Higher mSS was significantly associated with worse SF-36 PF (β = −0.10; 95% confidence interval [CI] −0.15 to −0.05) and HAQ (β = 0.003; 95% CI 0.002 to 0.004) after controlling for swollen joint count, sex, and disease duration. The number of damaged joints was associated with worse SF-36 PF (β = −0.23; 95% CI −0.38 to −0.08) and HAQ (β = 0.005; 95% CI 0.002 to 0.009). The presence of a damaged joint (grade 2–4) alone did not impact PF. However, the presence of a joint with grade 4 destruction was associated with substantially worse SF-36 PF (β = −3.04; 95% CI −5.93 to −0.15) and HAQ (β = 0.09; 95% CI 0.03 to 0.15). Increasing counts of grade 4 joints demonstrated a strong dose response with SF-36 PF (β = −0.54; 95% CI −0.81 to −0.26) and HAQ (β = 0.01; 95% CI 0.01 to 0.02).

Conclusion

Radiographic structural damage, particularly severe joint destruction, is independently associated with impaired PF in PsA, highlighting the importance of early detection and prevention of damage.