Biomechanical measures of lower limb variability, and prediction of non-contact knee injuries risk factors in male athletes

• Main Author: Alzhrani, M. M.
• Published: University of Salford 2018
• Subjects: 610
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.741156

Introduction: Football is one of the most popular sports played globally. Male players constitute 82% of football players around the world. As the number of football players increases, we expect more sports injuries to occur. Knee ligament injuries, such as Anterior Cruciate Ligament (ACL), are considered one of the most devastating injuries because of the consequences from the resulting damage. A large proportion of these injuries result from a non-contact mechanism. Some of the biomechanical risk factors in non-contact injuries are considered modifiable, therefore it is important to understand the mechanism of injury to modify it to be able to reduce or prevent the injuries. Also, recent studies have suggested that movement variability should be considered a potential source of information for analysis in monitoring athletes’ biomechanical performance. The aims of this thesis are to assess the performance and performance-variability of frontal plane projection angle (FPPA) and hip adduction angle difference between legs and over season, and its relationship with injury. Methodology: After assessing the validity and reliability of FPPA and hip adduction angle during single leg squat (SLS) and single leg landing (SLL) tasks, in a separate study with 15 healthy subjects, using the 2D technique, both tasks were found to be adequately valid and reliable in examining the lower limb kinematics. The main study then was done on 90 male professional footballers with the average age of 18.8±4 years, height 179.2±6 cm, and weight 73.3±6 kg, using SLS and SLL tasks to assess the performance and performance-variability of FPPA and hip adduction angle. The difference of performance and performance-variability of individual lower-limb kinematics (FPPA and hip angle) between legs and throughout the sports season (one year) were examined. Non-contact knee ligament injuries were also recorded. Then, the relationship between lower-limb kinematics (FPPA and hip angle) and injuries were investigated prospectively. Results: The performance of the dominant leg was found to be significantly more valgus (greater FPPA) than the non-dominant leg for both tasks in all screening sessions (-1.69° to -5.02° vs. 2.54° to -2.30°), but there was no difference in the hip adduction angle between legs (SLS, 73.15° to 73.47° vs. 74.53° to 75.85°; SLL, 80.91° to 83.55° vs. 81.58° to 85.39°). The overall performance of SLL FPPA (p = 0.01–0.0005) and hip angle (p = 0.0005) changed significantly over the collection time points. The difference in performance-variability between legs was not statistically significant for either FPPA or hip adduction angle in all of the screening sessions (p = 0.08–0.89), except for FPPA in the start-of-season screening. The performance-variability in FPPA and hip adducting angle were consistent over time (throughout the season) in both SLS and SLL (p = 0.13–0.61). Seven non-contact knee ligament injuries out of 75 total lower-limb injuries were reported. Therefore, a prediction analysis was not reported due to the limited obtained injuries. A descriptive analysis was carried out alternatively where injured legs performance and performance-variability showed similar actual scores in both tasks. However, after injury, a statistical test showed that the injured group’s performance of SLS and SLL did not change (p = 0.38–1), whereas the uninjured group’s performance of SLL did change significantly (p = 0.0005). The performance-variability of SLS and SLL did not change for both groups (p = 0.27–1), injured and uninjured. Conclusion: The difference of FPPA performance between legs in both tasks suggests that both legs need to be examined independently when assessing the lower-limb kinematics, rather than one leg alone or using bilateral tasks. Also, the change in FPPA and hip adduction angle over the sports season during SLL suggests that examining the lower-limb kinematics should be done regularly throughout the sport season due to the change of performance, rather than at one occasion. Also, it suggests that the SLL task is more sensitive than that of the SLS in detecting performance change. With regard to the performance-variability, it is unlikely to have a significant impact on overall performance. Finally, in light with predicting the non-contact knee ligament injuries using the 2D technique, larger number of injuries is needed to study this point.