Biomechanical characteristics of multidirectional single-leg landing

Single-leg landing (SLL) is a functional task that has been linked to injury. It is the test most used in both research and clinical practice to evaluate the dynamic stability of the lower extremities, particularly the knee joint. It is also an important screening tool that can be used to identify those who are at risk of lower-extremity injury and to evaluate the progress of rehabilitation regimes for individuals with lower-limb injuries. However, SLL occurs in multiple directions and from different heights during sport activity. Limited literature explores the biomechanical characteristics of SLL tasks and the association between different directions of SLL. A better understanding of SLL biomechanical characteristics and the relationship between different types of SLL may provide important information to help understand how individual joint biomechanics behave under different types of SLL to meet the demands of sport. Four themed studies are included in this thesis. The first study is a systematic review that aims to review the available literature that has investigated the biomechanics of the lower extremities during multidirectional SLL. The results indicate that only SLL in a forward direction is tested in the majority of the literature using three-dimensional (3D) motion analysis, indicating the importance of examining other directions that seen in sports or used clinically. The second study aims to examine within-day and between-days reliability and establish standard errors of measurement (SEM) for lower-extremity biomechanical variables using both two-dimensional (2D) and 3D motion analysis during multidirectional SLL. The majority of 2D and 3D variables show good to excellent reliability with relatively small SEM. However, knee valgus moment and hip adduction moment are less reliable among all the tasks assessed using 3D motion analysis. The third study investigates the correlation between 2D and 3D motion-analysis techniques when measuring the lower-extremity frontal plane of movement during multidirectional SLL. The results indicate that the 2D frontal plane projection angle (FPPA), at best, moderately correlates with 3D knee valgus angle, while the 2D hip adduction (HADD) angle shows strong significant correlation with 3D HADD angle, ranging between r = 0.70 to r = 0.90 across all tasks, apart from the right leg during medial single-leg landing off-platform, which had only a small association (r = 0.27), suggesting that 2D is a good alternative to 3D when measuring hip angles, though it should be used with caution when measuring knee angles. The final study examines the relationship between biomechanical variables during multidirectional SLL using both 2D and 3D motion-analysis techniques. The vast majority of 2D and 3D variables reported significant moderate to very strong correlations across all examined tasks. These findings suggest that a single task can be used to represent the biomechanical variables found across other tasks, so that when measuring lower-limb biomechanics, a clinician may not need to conduct all these tests. What this thesis adds to the current body of knowledge is that multidirectional SLL can be done in a reliable manner to measure lower-extremity biomechanical variables using either 2D or 3D motion analysis. 2D motion analysis can be used as a valid alternative to 3D, particularly for hip angle assessment, and single tasks can be used in isolation to represent lower-limb biomechanics across a multitude of tasks.