Is seeing just believing? Measurement properties of visual assessment of Postural Orientation Errors (POEs) in people with anterior cruciate ligament injury

Abstract: Rupture of the anterior cruciate ligament (ACL) is a common knee injury among young physically active populations. The injury results in impaired physical functions, such as joint instability, limitations in daily activities and sport-specific activities, and worse movement quality, e.g., altered postural orientation. Postural orientation is defined as the ability to maintain alignment between body segments, and undesirable postural orientation is suggested to be a risk factor for subsequent injury. The “gold standard” for measuring postural orientation is with three-dimensional motion analysis. However, there is a need for a systematic feasible approach to evaluate postural orientation in the clinical setting, such as with visual assessment. Therefore, the primary aim of this thesis was to develop and evaluate clinically feasible measures of postural orientation in participants with or without lower extremity injury. Secondary aims were to evaluate sex differences in postural orientation and the association between postural orientation and other measures of physical function and self-reported outcomes, in men and women undergoing rehabilitation after ACL reconstruction.One systematic review with meta-analysis was conducted to summarize measurement properties of visual assessment of postural orientation in healthy populations, and populations with lower extremity injury (paper I). Evaluation of measurement properties (i.e., face validity, interpretability, internal consistency, inter-rater reliability, and measurement error) of a test battery for visual assessment of postural orientation errors (POEs) in patients with ACL injury were reported in two cross-sectional studies (papers II–III). Sex differences in POE scores (i.e., total POE score, POE subscales activity of daily living (ADL) and sport, and segment-specific POEs across tasks) were investigated in one cross-sectional study (paper IV). In the same paper, the association between POE scores and hop performance and Patient-Reported Outcome Measures (PROMs) were evaluated, in men and women with ACL reconstruction, separately.This thesis shows that visual assessment of the segment-specific POE knee medial-to-foot position (KMFP) is associated with two-dimensional and three-dimensional kinematic variables, and shows moderate to almost perfect reliability for the KMFP in healthy populations. For other segment-specific POEs or for patients with lower extremity injury there were not enough studies to permit any synthesis. The evaluation of measurement properties (face validity, interpretability, and internal consistency) of visual assessment of POEs during a variety of functional tasks in patients with ACL injury, resulted in the final test battery of 5 functional tasks (single-leg mini squat, stair descending, forward lunge, singe-leg hop for distance, and side-hop) and 6 segment-specific POEs (foot pronation, KMFP, femur medial to shank, femoral valgus, deviation of pelvis in any plane, and deviation of trunk in any plane). Women demonstrated worse POE scores compared with men and worse POE scores were associated with worse hop performance in women (especially the POE subscale ADL), but not in men.The results from this thesis indicate that visual assessment of the segment-specific POE KMFP is valid and reliable in healthy populations. However, there is limited evidence of measurement properties for visual assessment of other segment-specific POEs, and in patients with lower extremity injuries. The test battery for visual assessment of POEs showed no floor or ceiling effects, high internal consistency, and good inter-rater reliability in patients with ACL injury. This indicates that visual assessment of POEs can be used in patients with ACL injury, both in research and in clinical practice. Furthermore, the results suggest that postural orientation should be evaluated separately for men and women, and that the POE subscale ADL could be used to help clinicians to decide when it is time to progress to jumping exercises during rehabilitation of ACL injuries.