The Relationship Among Pain, Intrinsic Capacity, and Fear of Movement in Patients with Knee Osteoarthritis: A Moderated Network Analysis.

OBJECTIVE: To investigate the relationship between intrinsic capacity (IC) and fear of movement, and to clarify how pain modified the relationship between IC and fear of movement at the symptom-level in patients with knee osteoarthritis (KOA). METHODS: In this cross-sectional observational study, 452 patients with KOA were recruited from a tertiary hospital in China. All participants completed validated self-report questionnaires to assess IC, pain, and fear of movement. Symptom-level network visualization and centrality analyses were conducted via moderated network analysis. The Johnson-Neyman technique was further applied to verify and quantify statistically significant moderated network edges. RESULTS: In the network, "somatic focus" was identified as the most central symptom (Expected Influence = 1.71), with the strongest association observed between "somatic focus" and "vision" (r = 0.62). Johnson-Neyman analysis revealed that pain significantly moderated the relationship between IC and fear of movement, including the edge between "psychological well-being" and "somatic focus" (t = -3.241, p < 0.01), and between "cognition" and "activity avoidance" (t = -2.740, p < 0.01). Additionally, higher pain strengthened the positive association between "avoidance beliefs" and "somatic focus" (t = 4.574, p < 0.001). CONCLUSION: Higher pain levels were associated with weaker relationships between selected intrinsic capacity domains and fear-of-movement dimensions. Targeted interventions integrating improved IC and pain management may represent a viable strategy to reduce fear of movement in patients with KOA, which requires confirmation in future longitudinal and intervention studies.