4. Discussion
The study sample, characterized by heterogeneous traumatic conditions as reported in
Table 1, provided the basis for exploring the relationship between sensor-based joint range of motion (ROM) measurements and multiple domains of patient functioning. Within this framework, the observed correlations across different joints and outcome measures offer insight into the construct validity of the assessment approach, highlighting how objective movement data relate to functional, performance-based, and psychosocial dimensions.
The correlations observed for the shoulder suggest a relationship between range of motion and specific functional and psychosocial domains, although this pattern appears to be selective rather than uniform across all measures. A significant association was found between mean right shoulder ROM and the activity avoidance component of the Tampa Scale for Kinesiophobia, indicating that reduced mobility may be linked to greater avoidance behaviors. This finding is consistent with the role of kinesiophobia in limiting movement through fear-related mechanisms, particularly in post-traumatic conditions [
25]. With regard to fatigue, significant negative correlations were identified between left shoulder internal rotation and overall fatigue severity, as well as between mean left shoulder ROM and FSS scores. These results suggest that reduced shoulder mobility may be associated with higher perceived fatigue, potentially reflecting increased effort required to perform upper limb activities in daily life [
26]. In the DASH analysis, the most consistent findings emerged in relation to the work domain. Specifically, right shoulder internal rotation and mean shoulder ROM were significantly associated with work-related disability, both in raw scores and percentage values. This is particularly relevant from a clinical perspective, as internal rotation plays a key role in many functional and occupational tasks involving reaching, handling, and positioning of the upper limb [
27]. Additionally, mean total shoulder ROM was associated with both the function/activity and work domains, supporting the idea that global shoulder mobility contributes to overall functional performance [
28]. It is important to note that these findings should be interpreted with caution due to the limited sample size for each scale (n = 12 for DASH, n = 10 for FSS, and n = 10 for TSK), which may have reduced the statistical power and contributed to the selective pattern of significant correlations observed.
The hip results showed a clearer and more consistent pattern than those observed for the shoulder, particularly across balance- and lower-limb-related outcome measures. The strong positive correlations with the Berg Balance Scale suggest that greater hip ROM is associated with better balance performance. This finding is clinically plausible, as hip mobility plays a central role in postural adjustments, weight shifting, and dynamic stability during functional tasks such as standing, turning, and transferring [
29]. The particularly strong association observed for mean total hip ROM further supports the idea that global hip mobility may be relevant to overall balance control. A similarly coherent pattern emerged with the LEFS, where greater hip ROM was associated with better lower extremity function. This is especially meaningful from a clinical perspective because the LEFS reflects perceived difficulty in everyday lower-limb activities, and many of these activities, such as walking, stair negotiation, bending, or changing position, depend substantially on adequate hip motion. The correlations observed with the KOOS also deserve attention. Although this scale was originally developed for knee-related symptoms and function, the significant associations found with hip ROM, particularly for the pain and activities of daily living domains, may indicate that restrictions at the hip influence the performance of tasks commonly captured by KOOS items, such as rising, walking, and other weight-bearing activities [
30]. The additional associations with sport and quality of life in some left hip movements suggest that reduced hip mobility may also be reflected in more demanding physical tasks and in patients’ perception of their musculoskeletal condition. With regard to the Tampa Scale for Kinesiophobia, the fact that significant correlations were limited to the activity avoidance component, rather than the total score or somatic focus, is clinically interesting. This may suggest that reduced hip ROM is more closely related to behavioral avoidance of movement than to the broader cognitive-emotional dimensions captured by the total scale. In practical terms, patients with more restricted hip mobility may be more likely to avoid activities that they perceive as physically demanding or potentially painful, especially those involving loading, stepping, or directional changes [
31]. Overall, the hip findings suggest that ROM measured with XClinic sensors may be particularly relevant in relation to balance, lower-limb function, pain-related activity limitations, and movement avoidance behaviors. From a clinical perspective, this supports the potential usefulness of instrumented hip assessment in capturing dimensions of functioning that are directly relevant both for rehabilitation planning and for multidimensional medico-legal evaluation.
The knee findings showed a coherent association between reduced ROM and several domains of patient-reported and performance-based functioning. The correlations with the KOOS were the most consistent, especially for pain, activities of daily living, sport/recreation, and, to a lesser extent, quality of life. This pattern is clinically meaningful because the KOOS was specifically designed to capture knee-related symptoms and their impact on daily and more demanding activities, so its association with instrumentally measured knee ROM supports the functional relevance of the sensor-based assessment [
20]. The fact that significant correlations were observed not only for individual movements, particularly left knee flexion, but also for mean knee ROM values suggests that both specific and global restrictions in knee mobility may be reflected in patients’ perceived knee-related difficulties [
32]. A similar, although more selective, pattern emerged for the LEFS, which reflects difficulty in performing everyday lower-extremity tasks. Significant associations with right knee flexion, right knee extension, and mean knee ROM values suggest that better knee mobility may be linked to better lower-limb function in activities such as walking, transfers, and stair negotiation [
21]. The positive correlations with the Berg Balance Scale, particularly for right knee flexion and mean right and total knee ROM, are also clinically plausible, since the Berg assesses functional balance through tasks that require controlled knee motion during standing, transfers, turning, and stepping. The associations with the Tampa Scale for Kinesiophobia were limited to left knee flexion, but they involved the total score as well as both subdomains, activity avoidance and somatic focus. This may suggest that, in this sample, restricted knee flexion was related not only to behavioral avoidance of movement but also to greater concern about bodily vulnerability and pain-related harm. The isolated correlation between left knee flexion and the FSS may indicate that limitations in a movement that is central to many daily tasks are accompanied by higher perceived fatigue, whereas fatigue was not broadly associated with the other knee ROM variables. Overall, these findings suggest that knee ROM measured with XClinic sensors may be particularly relevant to pain-related function, balance performance, lower-extremity activity, and selected psychological and fatigue-related dimensions [
33].
The ankle findings showed a more selective pattern of associations than those observed for the hip and knee, but the significant correlations still point to clinically meaningful links between ankle mobility and lower-limb performance. The positive correlations with the Berg Balance Scale, particularly for right plantar flexion and right eversion, suggest that greater ankle ROM may support better balance performance. This is plausible because the Berg evaluates tasks such as standing, turning, reaching, and transfers, all of which require adequate ankle control to maintain postural stability [
34]. Similarly, the significant correlations with the LEFS indicate that better right ankle mobility, especially in plantar flexion, eversion, and inversion, was associated with better self-reported lower-extremity function; this is consistent with the purpose of the LEFS as a measure of difficulty in everyday lower-limb activities [
21]. The correlations with the Tampa Scale for Kinesiophobia were limited to specific movements and specific subdomains rather than the total score. Left plantar flexion was associated with activity avoidance, whereas right eversion was associated with somatic focus, suggesting that restricted ankle motion may relate either to avoidance of movement-based activities or to greater concern about bodily vulnerability, depending on the movement involved [
35]. The significant associations with the FSS were also movement-specific, involving left inversion and right eversion. Since the FSS captures the perceived impact of fatigue on functioning, these findings may indicate that restrictions in ankle motions involved in stabilization and gait adaptation are accompanied by greater fatigue-related burden during daily activities, even if this association was not reflected by mean ankle ROM values. Overall, the ankle results suggest that sensor-based ROM assessment may be especially relevant for domains related to balance, lower-extremity activity, and selected psychological and fatigue-related aspects of functioning, although the associations appear less widespread than those found for the hip and knee. From a clinical perspective, this may reflect the more task-specific contribution of ankle mobility, where particular movements become relevant depending on the functional demand being considered [
36].
4.1. Medico-Legal Implications
From a medico-legal perspective, the present findings suggest that instrumented assessment of joint range of motion may provide additional, objective information that complements traditional evaluation methods based on clinical examination and patient-reported outcomes. The observed associations between sensor-derived ROM and multiple domains of functioning, including balance, lower-limb activity, and selected psychosocial factors, indicate that these measurements may reflect aspects of functional impairment that are relevant to the overall assessment of biological damage.
In particular, the relationship between ROM and outcome measures related to daily activities and work-related function may support a more comprehensive evaluation of the impact of trauma on an individual’s functional capacity. This could be of potential interest in medico-legal contexts, where the estimation of damage increasingly requires consideration of real-life functioning and participation, rather than relying exclusively on anatomical or impairment-based criteria [
37].
At the same time, these results should be interpreted with caution. The variability in sample size across different joint–scale combinations and the cross-sectional nature of the study limit the possibility of drawing definitive conclusions regarding the role of sensor-based measurements in medico-legal decision-making. Furthermore, the selective pattern of correlations observed across joints suggests that the relationship between objective movement data and functional outcomes may depend on the specific anatomical region and the type of activity considered. Future studies with larger and more homogeneous samples are needed to further explore the potential integration of wearable sensor data into medico-legal assessments. In particular, longitudinal designs could help clarify whether these measures are sensitive to changes over time and whether they can contribute to a more accurate estimation of functional prognosis and long-term care needs.