Posttraumatic osteoarthritis after ACL rupture: identifying clinical targets for rehabilitation
Date
2022
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
Anterior cruciate ligament (ACL) injuries are among the most common traumatic knee joint injuries. An estimated 250,000 ACL reconstructions (ACLR) are performed each year in the United States alone. After ACLR, outcomes are highly variable, with an increased risk for second injury, reduced rates of returning to preinjury sport or activity level, and increased risk of developing posttraumatic knee osteoarthritis (PTOA). Approximately 50-80% of individuals go on to develop PTOA within 5-15 years, regardless of surgical or nonsurgical management. The average individual who sustains an ACL injury is young and active, with most individuals on track to develop early onset PTOA in young adulthood. Early development of knee osteoarthritis is associated with reduced sports and recreational participation, pain, lower self-reported quality of life, and premature total knee arthroplasty. These long-term consequences of ACL rupture can be life-altering to the individual who has sustained a rupture. ☐ Though the development of PTOA is not fully understood, there are some identified risk factors such as reduced functional performance, return to participation in high-level sport, and walking with asymmetric knee joint mechanics and loading. Considering the statistics regarding return to sport, reinjury, and PTOA, it is clear there are individuals who have poor long-term outcomes after ACL rupture. However, there are also some individuals who are successful in returning to sport and avoiding some of the most devastating long-term outcomes. It is important, therefore, to begin to identify each type of patient, as being able to classify individuals may help explain variability in outcomes. If we can identify subgroups of individuals, we can assess the factors that may characterize each subgroup and pinpoint rehabilitation strategies for each group, moving ACL rehabilitation more towards a precision-rehabilitation approach. ☐ Undergoing ACLR does not normalize the asymmetric knee biomechanics related to developing PTOA (e.g., reduced knee flexion excursion, reduced knee extensor moment). Current clinical interventions and evidence-based rehabilitation programs have not been successful in restoring symmetric gait mechanics, therefore, there is a need to develop rehabilitation strategies to address gait after ACLR. Further, ACL rupture and reconstruction have neuromuscular implications and alter afferent input to the central nervous system (CNS). Clinical interventions often rely on the adaptive properties of the CNS to learn new movement patterns, so it is critical to understand if there is CNS flexibility in individuals who have undergone ACLR. ☐ The primary goal of this dissertation was to further explore clinical and biomechanical factors that characterize those on track to develop PTOA after ACL injury. Aim 1 leveraged the 5-year time point of an ongoing cohort study to explore the association of quadriceps strength symmetry and surgical status (i.e., operative or nonoperative management) with early clinical knee PTOA at 5 years after ACL injury. We used clinically-available criteria proposed by an international consensus statement to classify those with ‘osteoarthritis’ or ‘no osteoarthritis,’ allowing for direct clinical utility of our results. Aim 2 used baseline data (n=300) from the same ongoing cohort study to 1) identify existing baseline subgroups of ACL injured individuals based on patient characteristics, patient-reported outcome measures, and functional performance and 2) determine associations between subgroups and the development of radiographic PTOA 5 years after ACL rupture. Finally, Aim 3 (1) examined the ability of individuals after ACLR to adapt the aberrant knee joint mechanics related to PTOA development using a split-belt treadmill paradigm and (2) compared the extent of adaptation to uninjured, age-matched individuals. ☐ As physical therapists, we currently lack clinical targets appropriately addressing the development of PTOA after ACLR. This dissertation was among the first to look for associations between quadriceps strength at 5-years and clinical PTOA, and the first to use a subgroup-based approach to identify clinical targets for interventions during rehabilitation after ACL rupture. Further, this dissertation was one of the first to leverage well-studied principles from split-belt adaptation paradigms to study the adaptability of gait mechanics in individuals after ACL reconstruction. Ultimately, findings from this dissertation will inform the development of clinical interventions directly targeting the proposed mechanisms association with PTOA after ACLR.
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Keywords
ACL, Post-traumatic osteoarthritis, Rehabilitation