Temporal Associations Between Pain Intensity and Disturbed Body Perception After Total Knee Arthroplasty: A Random-Intercept Cross-Lagged Panel Model Analysis

Knee osteoarthritis is a common cause of pain and disability, and total knee arthroplasty (TKA) is frequently performed to improve symptoms and function. Although many people experience substantial improvement after surgery, a subset report ongoing pain during recovery. Disturbed body perception (e.g., reduced clarity, altered awareness, or a sense that the knee feels unfamiliar) has been associated with persistent musculoskeletal pain, but the temporal ordering of postoperative pain and knee-specific body perception after TKA remains unclear.

This observational cohort study follows adults undergoing primary TKA and examines longitudinal associations between pain intensity (during movement and at rest) and knee-specific body perception across the first postoperative year. Participants complete brief self-report questionnaires at preoperative baseline and at multiple postoperative follow-up time points through 12 months. Clinical care (surgery, analgesia, and rehabilitation) is provided as usual and is not altered by study participation; the study procedures involve completion of questionnaires only.

The primary objective is to evaluate whether within-person changes in knee-specific body perception are prospectively associated with later within-person changes in pain intensity over time, while accounting for stable between-person differences. Longitudinal analyses will use random-intercept cross-lagged panel modeling to separate trait-like, between-person stability from state-like, within-person fluctuations and to estimate autoregressive and cross-lagged associations across adjacent waves. Missing questionnaire data will be handled using full-information maximum likelihood under a missing-at-random assumption, and sensitivity analyses will be conducted using the complete-case sample to evaluate robustness. Descriptive summaries and correlations will be used to characterize the observed trajectories and concurrent associations across time points.

The study is conducted in accordance with institutional ethical approval and written informed consent. Data are managed confidentially in line with institutional policies, and analyses are performed on de-identified data whenever possible. Findings are intended to inform future research on potentially modifiable factors related to persistent pain after TKA and to support development of rehabilitation strategies that may incorporate body perception-related approaches.