Graduation Semester and Year




Document Type


Degree Name

Doctor of Philosophy in Kinesiology



First Advisor

Mark D Ricard


Joint loading of the lower extremity is studied to identify risk factors for anterior cruciate ligament (ACL) injuries and to determine limb asymmetries. Asymmetrical loading in the lower extremity during ACL reconstruction (ACLR) rehabilitation and at the time of return to sport or activity will cause compensations during functional movements, which can lead to unwanted joint re-injury or long-term joint damage. Re-injury and/or development and progression of knee osteoarthritis (OA) is prevalent after ACLR; therefore, joint loading measurements at extended time points from reconstruction and after return to play may help to identify how asymmetrical loading and compensatory movement strategies contribute to these occurrences. The joints of the lower extremity experience different stresses when ACLR individuals return to physical activity after clearance from rehabilitation because there are varying intensities and physical demands on individual athletes. Individuals also may actually avoid loading their ACLR knee because of persistent symptoms, poor perception, or limited knee extensor eccentric control . Therefore, our understanding of the impact of both excessive and limited knee joint loading on knee OA can be developed from an understanding of the normal and abnormal lower extremity movement patterns or strategies during various functional tasks in ACLR individuals. Study 1 (Chapter 2) takes a comprehensive approach to understand the difference in joint loading by way of energy absorption (EA) and energy absorption contribution (EAC) during three different functional tasks, single-leg squat (SLS), single-leg hop, and gait, in ACLR individuals 2-9 years removed from surgery and healthy, matched control participants. Advanced statistical analyses were used to identify interaction effects between each task within each group and between groups. There were differences between both groups in EA and EAC across all joints when comparing each physical performance task. Knee joint loading was greatest for both groups during the SLS task. ACLR participants utilized strategies with greater hip compensations during hop tasks and greater ankle contribution during gait tasks. These findings suggest the ability of ACLR participants to utilize altered loading strategies when performing different functional tasks and likely represent an avoidance of loading the knee of the surgical limb. The avoidance of knee joint loading in ACLR subjects are likely due to strength and range of motion asymmetries in the surgical limb compared to the non-surgical limb within ACLR subject as well as the matched limb within the healthy controls. Physical performance on different functional tasks is not only related to physical capacity but it is also related to a patient’s self-efficacy related to the task, so it is important to measure a patient’s perception of their capabilities as these cannot be objectively proven with lab tests. Self-reported function (SRF) has been utilized in conjunction with other biomechanical measures to explain kinetic and kinematic alterations; however, the comparison to EA and EAC has not been explored. Study 2 (Chapter 3) used performance on the previously mentioned physical performance tasks to identify an interaction effect with SRF, as measured by the Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) forms. Overall, across functional tasks, ACLR subjects with lower SRF also used joint loading strategies that limited knee loading and emphasized hip and ankle compensations. These data support the notion that a lower perception of function will lead to changes in energy absorption. When compared to control subjects, ACLR subjects with SRF in either low or high sub-groups consistently demonstrated altered loading strategies with more ankle and/or hip contribution in an effort to underload the knee. The findings of these investigations provide insightful information into energy absorption measures of joint loading within a variety of functional tasks in a previously unstudied time frame (2-9 years) following ACLR. Movement asymmetries and deficits in joint loading will impact knee joint health and the inclusion of measures of SRF are a necessary compliment to objective findings as understanding how ACLR individuals perceive their ability to load their surgical knee may help our understanding of asymmetrical loading patterns. Future work should identify EA and EAC across other performance tasks, in addition longitudinal investigations of joint loading and SRF in ACLR patients beyond the typical continuum of care from surgery through rehabilitation and return to activity should be pursued.


ACL, Joint loading, Self-reported function


Kinesiology | Life Sciences


Degree granted by The University of Texas at Arlington

Included in

Kinesiology Commons