Graduation Semester and Year
Summer 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Kinesiology
Department
Kinesiology
First Advisor
Mark Ricard
Second Advisor
Sophia Ulman
Third Advisor
Meredith Decker
Fourth Advisor
Stephen Newhart
Fifth Advisor
Matthew Brothers
Abstract
Anterior cruciate ligament (ACL) injuries are a significant concern in adolescent female athletes, with rates consistently higher than their male peers. This disparity is attributed to a complex combination of anatomical, hormonal, and neuromuscular factors that elevate injury risk while performing dynamic movements common in running and cutting sports such as soccer, basketball, lacrosse, and volleyball. Knee laxity has been identified as a potential risk factor, yet current measurement tools lack the sensitivity, reliability, and validity needed for practical application. Additionally, fluctuating sex hormones throughout the menstrual cycle (MC) have been implicated in changes to ligament properties and neuromuscular control, but evidence remains inconsistent. Addressing these knowledge gaps, this dissertation investigates ultrasonographically measured knee laxity and biomechanical movement patterns and adolescent female athletes, with particular attention to differences across MC need some phases. By integrating novel ultrasonographic techniques with three-dimensional motion capture, this research aims to clarify the relationship between knee laxity and biomechanical risk factors, and to determine whether these variables vary significantly across MC phases.
Chapter 1 establishes the theoretical and empirical foundation for examining ACL risk and adolescent females, focusing on the relationship between knee laxity measured by dynamic ultrasound with a novel prone Lachman technique along with lower-extremity biomechanics, assessed using 3D motion capture, during a single-leg hop in adolescent female athletes. Twenty-three participants between the ages of 13- to 17-years-old who had not experienced any major knee injury or surgery were included in the final analysis. Greater anterior knee displacement was significantly associated with reduced ankle dorsiflexion moments and greater external knee rotation, while greater posterior knee displacement was associated with reduced ankle dorsiflexion, increased hip external rotation moments, and reduced knee external rotation. These findings suggest that increased knee displacement influences compensatory load distribution across the ankle, knee, and hip. While these adaptations may help stabilize the knee joint, they can increase stress on surrounding joints and elevate te risk of lower-extremity injury. Overall, these results highlight the need to assess both structural and biomechanical factors to better understand ACL injury risk in adolescent female athletes.
Female athletes are at a greater risk of sustaining an ACL injury compared to their male peers. Risk for youth begins increasing as they approach adolescence around 10- to 12- years old. Studies investigating changes in biomechanical risk and knee laxity across the menstrual cycle have been conducted with adult and professional female athletes, but results have been conflicting and inconclusive. Furthermore, there is gap in research concerning effects of the menstrual cycle and adolescent athletes’ risk for sustaining an ACL injury. Chapter 2 investigates differences in knee laxity and biomechanics across the early follicular, ovulatory, and mid-luteal phases of the menstrual cycle in adolescent female athletes. Thirty-two adolescent female athletes who were not actively using any form of hormonal birth control, had been experiencing menstrual cycles for a minimum of two years, and had not sustained a major knee injury or undergone any significant surgery. Menstrual cycle phases were determined using a calendar-based method. Knee laxities were measured using dynamic ultrasound with the prone Lachman and 3D motion capture was used to assess biomechanical risk during a single leg hop (SLH). The early follicular phase showed significantly greater anterior displacement as well as increased hip internal rotation angles and coronal knee moments. These findings indicate structural and functional ACL risk factors vary with menstrual phase with periods of heightened vulnerability due to increased risk and less favorable biomechanics.
This work provides novel insight into phase-dependent variations in knee laxity and biomechanics in adolescent female athletes. Combining dynamic ultrasound with 3D biomechanical analysis identifies modifiable risk factors that may guide timing and design of neuromuscular training. Future research should examine these relationships longitudinally, incorporate hormonal verification for precise phase classification, and test whether phase-specific interventions can reduce ACL injury risk in this high-risk population.
Keywords
ACL injury, adolescent female athlete, menstrual cycle, knee laxity, dynamic ultrasound, prone Lachman test, 3D motion capture
Disciplines
Biomechanics | Sports Medicine
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Garcia, Jessica, "Menstrual Cycle Variations in Ultrasound and Biomechanical Risk Factors for ACL Injury in Adolescent Female Athletes" (2025). Kinesiology Dissertations. 49.
https://mavmatrix.uta.edu/kinesiology_dissertations/49