Date of Award
Doctor of Physical Therapy (DPT)
Introduction: Literature has consistently reported a high prevalence of ACL injury rates. A correlation between excessive subtalar joint pronation and ACL injury rates has been noted but research into plausible reasons for this relationship is limited. The purpose of this study was to establish potential cause-and-effect relationships between foot position and ACL injury risk.
Methods: This study used single leg squats with simulated foot positions and examined resulting knee joint forces from motion and lower extremity muscle activation patterns that may cause ACL injury risk. Methods: This study recruited male and female participants aged 18 to 30 from campus at the University of North Dakota. Subjects performed single-leg-squats with simulated foot positions using varying degrees of inclination while EMG electrodes recorded muscle activity and reflective markers tracked motion. ANOVA tests were run to compare individual muscle activity between subjects with identical foot positions as well as to compare identical foot positions and resulting gross muscle activity between subjects.
Results: This study was unable to produce significant results regarding differences in muscle activation patterns as a function of foot position. Significance of differences among subjects’ individual muscle activity with varying foot positions ranged from p = .299 to .749 (alpha = .05). Significance of difference between subjects’ gross muscle activity as a function of varying foot positions ranged from p = .462 to .992 (alpha = .05).
Discussion: This study had excessive variance between subjects due to number of participants and should be continued in an attempt to identify significant results unattainable to this point. Significant results could describe causative factors for the correlation between excessive pronation and high rates of ACL injury. Understanding these factors could be useful in the field of physical therapy to guide practicing clinicians in establishing appropriate ACL injury rehabilitation and prevention interventions.
Conclusion: No cause-and-effect relationships between foot position with resulting lower extremity muscle activation patterns and ACL injury risk could be postulated due to insignificant differences. Additional research is needed to examine the correlation between these two variables.
Debele, Brett J., "Muscle Activity in Lower Extremity During Single-Leg Squat: Role of Supination and Pronation" (2011). Physical Therapy Scholarly Projects. 618.