Background/Purpose: Mechanical stress is known to trigger and exacerbate psoriatic arthritis (PsA). Based on the hypothesis that biomechanical stress is greater in the dominant extremity, we aimed to investigate the association between handedness and radiographic damage in PsA.

Methods: We included PsA patients from a prospective observational cohort. Handedness was determined by self-report of the writing hand. To assess the relationship between handedness and peripheral joint damage, we used linear mixed models (LMMs) with the modified Steinbrocker score (mSS) as the outcome. We studied the association of handedness with total mSS, total hand or foot mSS, single-sided mSS, and single-sided hand or foot mSS. As no known confounders exist between the exposure (handedness) and the outcome (radiographic damage), models were adjusted only for variables that were imbalanced between groups and are known to be associated with peripheral damage.

Results: Among 359 patients, 324 (90.3%) were right-handed and 35 (9.7%) were left-handed (Table 1). At baseline (clinic entry), the mean (SD) age was 43.7 (12.9) years. Compared to right-handed individuals, left-handed patients were older, had longer psoriasis duration, and higher BMI. In LMMs adjusted for these variables (Figure 1 and Table 2), left-handedness was associated with a trend toward higher total mSS (β = 7.59, 95% CI -0.88 to 16.07). A significant association was observed with higher total hand mSS (β = 6.34, 95% CI 0.24 to 12.22). Similar trends were seen in side-specific analyses: left-handedness was associated with higher mSS on both right and left sides (β = 3.82, 95% CI -0.54 to 8.17; β = 3.79, 95% CI -0.52 to 8.09, respectively). Notably, left-handedness was linked to significantly higher left-hand mSS (β = 3.37, 95% CI 0.25 to 6.48), whereas the association with right-hand mSS was weaker (β = 2.98, 95% CI -0.17 to 6.13). Associations with foot mSS—both unilateral and bilateral—were less pronounced.

Conclusion: In PsA, where right-handedness predominates, left-handed individuals appear to experience greater peripheral joint damage, particularly in the hands, with a stronger effect observed in the left hand. Mechanical stress from daily activities—shaped by tools and environments predominantly designed for right-handed individuals—may contribute to this pattern. Potential cross-laterality (e.g., left-handedness with right-foot dominance) may attenuate observed patterns of foot involvement.

Table 1. Baseline characteristics (clinic entry).

Table 2. Linear mixed models analyzing the association between handedness and peripheral damage.

Figure 1. DAG showing the relationship between the exposure (handedness) and outcome (peripheral damage) in our model.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-association-of-handedness-with-radiographic-damage-in-patients-with-psoriatic-arthritis/