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

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 using modified Steinbrocker score (mSS, 0‐168). Associations between PF and mSS were analyzed using linear mixed models. We also evaluated the impact of presence of any damaged joint (grade 2‐4), joint damage by individual grades, and number of damaged joints (grade 2‐4) per patient on PF. Results Of 1177 patients (mean age 44.61 ± 12.76 years; 55.8% males), baseline mSS was 2 (IQR 0‐8.5), HAQ 0.62 (0.12‐1.12), and SF‐36 PF 60 (35‐85). Higher mSS was significantly associated with worse SF‐36 PF ( β= ‐0.10; 95%СI ‐0.15, ‐0.05) and HAQ (0.003; 0.002, 0.004) after controlling for swollen joint count, sex, and disease duration. The number of damaged joints was associated with worse SF‐36 PF (‐0.23; ‐0.38, ‐0.08) and HAQ ( 0.005; 0.002, 0.009). The presence of a damaged joint (grade 2‐4) alone didn't impact PF. However, the presence of a joint with grade‐4 destruction was associated with substantially worse SF‐36 PF (‐3.04; ‐5.93, ‐0.15) and HAQ (0.09; 0.03, 0.15). Increasing counts of grade‐4 joints demonstrated a strong dose response with SF‐36 PF (‐0.54; ‐0.81, ‐0.26) and HAQ (0.01; 0.01, 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.