Main author: Guðni Rafn Harðarson
Institution or Company: Háskóli Íslands
Co-Authors, Institution or Company:
Kristin Briem, Háskóli Íslands. Haraldur Björn Sigurðsson, University of Delaware.
Introduction: Dynamic Valgus (DV) characterized by hip -adduction (HA), -rotation (HR) and knee abduction (KA), is considered an important risk factor of knee injuries [1], which can affect the career of athletes [2]. Identifying DV is done using a drop-jump (DJ) with expensive three-dimensional (3D) motion-capture [3]. Visual-assessment of medial-knee displacement (MKD) requires less effort. This project aimed to assess if MKD is associated with components of DV.
Methods: Prospective laboratory study. Participants (n=283, age=9-12) performed DJs and those available returned 4-6 years later (n=177, age=14-18). Data was recorded with an eight-camera motion-capture system. MKD was the displacement of the distal-femur from initial-contact to its maximum medial-position before the lowest-position of the pelvis during landing. Changes in HA, HR and KA were taken for the period. A mixed linear model was created, MKD normalized by femur length as the dependent-variable, joint-movement, leg and phase as independent-variables.
Results: An association was found between the DV variables and MKD ranging from 0.0164 femur lengths per 10° of HA to 0.007 for KA (P<0.01). R^2 was 0.36 and the fixed-effects coefficient was 0.167.
Conclusion: The model only explained 16.7 percent of the variability in MKD and, therefore, does not support the use of MKD.
References
[1] Mehl, J. et al. (2018). Arch Orthop Trauma Surg, 138(1): 51–61.
[2] Ross, B. J. et al. (2020). Orthop J Sports Med 8(10).
[3] Lima, Y. L. et al. (2018). Phys Ther Sport 29: 61–69.
