Background: Rheumatic and musculoskeletal diseases (RMDs) affect 1.7 billion people globally, representing the leading cause of disability across all age groups. Functional decline begins years before pain prompts clinical presentation, yet by the time patients seek care, reversing deterioration becomes significantly more challenging. Traditional screening relies on symptom-based questionnaires or specialist assessment, limiting population-level prevention. Digital functional assessment offers scalable screening but requires validation. Understanding whether physical activity or pain better predicts musculoskeletal capacity has important implications for prevention strategies and early intervention targeting.

Objectives: To validate a digital four-domain musculoskeletal screening tool using known-groups methodology, examining whether physical activity or pain status better predicts functional capacity. Secondary Objectives: identify risk stratification thresholds and explore gender differences in pain-function relationships.

Methods: Retrospective study of 243 working adults (mean age 42.4 years, 58% female) completing digital assessments via workplace programmes (October-November 2025). Tool evaluated strength (30-second squat), balance (single-leg stance), flexibility (toe-touch, back-scratch), and dynamic posture (overhead squat) via self-administered web interface. Known-groups validation compared high-activity (≥3 sessions weekly, n=61) versus low-activity (≤1 weekly, n=37), and pain-free (n=35) versus moderate-severe pain (≥4/10, n=66). Analyses: Mann-Whitney U tests, Cohen’s d (0.2=small, 0.5=medium, 0.8=large), ROC curves, Youden’s Index. Gender and age examined as moderators.

Results: Among 143 completers (58.8% completion rate), physical activity showed superior discriminative validity. High-activity individuals scored 12.35 points higher than low-activity (76.5 vs 64.1, p<0.001, d=0.889), substantially exceeding pain effects (pain-free 74.7 vs pain 67.5, p=0.034, d=0.447). The activity effect was approximately twice that of pain effects. Activity benefits persisted across ages 20-39 (d=0.824, p<0.001) and 40-59 (d=0.926, p<0.001), demonstrating physical activity confers functional advantages regardless of age. Domain-specific analyses revealed significant activity effects in strength (p=0.011, d=0.510), balance (p=0.004, d=0.606), and flexibility (p=0.0003, d=0.760) domains. Critically, low-activity workers with minimal pain showed marked impairment versus active peers, representing a high-risk phenotype missed by symptom-based screening (approximately 26% of workforce). These asymptomatic yet functionally impaired individuals are optimal early-intervention targets before clinical deterioration necessitates medical care. ROC analysis identified optimal threshold at score <67 (specificity 93.8%, sensitivity 73.7%, LR+ 11.9, OR=42.0, 95% CI 8.9-198.2, p<0.0001). Among 100 workers scoring <67, approximately 94 require intervention, enabling efficient resource allocation in population health programmes. A striking and previously unreported gender interaction emerged (p=0.006). Pain substantially impaired male function (pain-free 76.3 vs pain 64.9, 11.42-point reduction, p=0.035, d=0.700) but had negligible impact on female function (pain-free 72.4 vs pain 71.2, 1.21-point reduction, p=0.664, d=0.085). This differential pain-function coupling persisted after adjusting for activity and age, suggesting biological or behavioural sex differences in how pain influences motor performance during functional testing. Pain severity affected completion rates: pain-free 68.9% versus severe pain 42.9% (p=0.0025), indicating pain acts as participation barrier.

Conclusions: This study provides validation evidence for digital screening that successfully identifies workers at elevated RMD risk before symptom onset. Physical activity emerges as a stronger, more modifiable predictor of functional capacity than pain (effect size nearly double), supporting paradigm shift from reactive symptom management to proactive capacity-based screening in occupational health and public health prevention programmes. Low-activity workers with minimal pain represent critical yet overlooked early-intervention targets. These individuals show functionally significant deficits placing them at elevated RMD risk, yet lack symptoms prompting healthcare-seeking or triggering identification through symptom-focused protocols. Early detection enables intervention when functional restoration is most achievable and cost-effective. The validated threshold (score <67) provides evidence-based criteria for risk stratification with excellent specificity, enabling efficient allocation of prevention resources. Digital self-administered format addresses scalability barriers, facilitating deployment across workplace, primary care, and community settings without requiring clinician time. The novel gender-specific pain-function relationship has direct implications for RMD assessment and rehabilitation. Pain serves as a reliable functional impairment indicator in males but not females, suggesting sex-stratified interpretation frameworks may be necessary to optimize detection and avoid gender-based misclassification of RMD risk. This striking differential warrants mechanistic investigation into biological differences in pain processing, sex-specific neuromuscular control strategies, or gendered behavioural responses during assessment. Findings align with public health and rheumatology priorities emphasizing prevention, early detection, and modifiable risk factor modification for reducing global RMD burden. Digital capacity-based screening enables population-level implementation with potential for reducing healthcare costs and disability burden through proactive intervention.

REFERENCES: NIL.

Acknowledgments: NIL.

Disclosure of Interests: None declared.