Brain volume alterations in patients with chronic knee-joint injury: A cross-sectional analysis based on vehicle-mounted mobile magnetic resonance imaging data

Abstract

Although chronic musculoskeletal pain is reportedly associated with changes in brain structural plasticity, the controlled settings of most studies to date may not reflect the brain characteristics of patients in weight-bearing conditions. Recent advances have enabled non-invasive research into the neuro-musculoskeletal relationship using vehicle-mounted mobile magnetic resonance imaging. The present study aimed to investigate specific brain region volumes among participants with chronic knee-joint injury from a specialized occupational group undergoing high-intensity regular training. A cross-sectional study was conducted from October to December 2024, and 179 individuals from high-physicaldemand occupations were retrospectively included. Subjects were stratified based on occupational exposure duration–short-term (< 3 years), and longterm (≥ 3 years)–to enable subgroup analyses. Comprehensive data, including demographic details, clinical histories, knee joint assessments, brain images acquired using volumetric magnetic resonance imaging with three-dimensional T1-weighted sequences (to quantify regional brain volumes), and psychological assessments (e.g., Athens Insomnia Scale and fatigue metrics), were collected. All 179 enrolled participants were male, with a mean age of 27.37 ± 5.01 years; they comprised 116 patients with chronic knee-joint injury and 63 healthy controls. Compared with healthy controls, the chronic knee-joint injury group showed smaller volumes of left parahippocampal gyrus and right superior frontal gyrus, but a larger volume in the right inferior lateral ventricle (all P < 0.05). Correlation analyses between regional brain volumes and psychological scale scores revealed significant differences between patients with chronic kneejoint injury and healthy controls. In patients with chronic knee-joint injury, higher Athens Insomnia Scale scores were associated with smaller bilateral thalamic volumes ( P < 0.01). Moreover, habitual sleep efficiency was negatively correlated with the volumes of the bilateral white matter, left entorhinal cortex, and left inferior temporal gyrus (all P < 0.01) but was positively correlated with the volumes of the right entorhinal cortex and right inferior temporal gyrus (both P < 0.01). In patients with chronic knee-joint injury, higher physical fatigue scores were associated with larger right superior parietal lobule volume ( P < 0.01), whereas fatigue self-assessment scale scores were negatively correlated with the volume of the left thalamus, cerebrospinal fluid, right isthmus of the cingulate gyrus, and right lingual gyrus (all P < 0.01). By contrast, in healthy controls, multiple fatigue measures (physical fatigue, mental fatigue, fatigue consequences, and fatigue self-assessment scale scores) were significantly positively correlated with brainstem volume only (all P < 0.01). Additionally, occupational exposure years in patients with chronic knee-joint injury were positively correlated with the volume of the right triangular gyrus ( P < 0.01). Subgroup analysis revealed that, among subjects with short-term occupational exposure, significant volume differences were observed in the isthmus of the cingulate cortex and the caudate nucleus between patients with chronic knee-joint injury and healthy controls (both P < 0.05), whereas among those with long-term exposure, significant differences were only observed in the ventricular region ( P < 0.05). Collectively, these findings indicate a specific pattern of neuroanatomical changes unique to patients with chronic knee-joint injury in a specific occupational population. Alterations in their brain volume were observed in the right inferior lateral ventricle, left parahippocampal gyrus, and right superior frontal gyrus, and these changes were not associated with psychological or cognitive factors.