Individuals who sustain an anterior cruciate ligament (ACL) injury and undergo subsequent ACL reconstruction (ACLR) frequently experience psychological responses to their injury. Increased injury-related fear post-ACLR has been found to be associated with neuroplastic adaptations and injury-related outcomes including perceptual-motor coordination (P-MC) and landing biomechanics. However, limited evidence has explored the impact of pain-related psychological responses, such as pain catastrophizing, on neural function and injury-related outcomes in individuals with ACLR. Understanding the association between pain catastrophizing and neural mechanisms that may contribute to functional and injury-related outcomes after ACLR could allow for identification of modifiable factors that, if addressed throughout rehabilitation, may positively influence clinical outcomes and secondary injury risk among individuals with ACLR. Therefore, the purposes of this three-study dissertation were to: 1) examine the influence of pain catastrophizing on lower extremity perceptual-motor coordination (P-MC) after ACLR, 2) explore the relationship between pain catastrophizing and neural activity in individuals with ACLR, and 3) examine the influence of pain catastrophizing on changes in P-MC and jump-landing biomechanics in a setting with distractions that mimic a sport environment in individuals with ACLR. In the first cross-sectional study assessing the influence of pain catastrophizing on lower extremity P-MC, 45 individuals with ACLR completed the Pain Catastrophizing Scale (PCS) and a lower extremity P-MC task with the ACLR limb and contralateral limb using a series of wireless light discs. Separate multiple regression analyses identified that pain catastrophizing was not associated with ACLR limb P-MC (β=0.002, p=0.247) or contralateral limb P-MC (β=0.001, p=0.410) in individuals with ACLR. These findings indicate that pain catastrophizing may not contribute to lower extremity perceptual-motor function after ACLR. In the second study exploring the relationship between pain catastrophizing and neural activity, 15 individuals with ACLR completed the PCS and underwent full brain functional magnetic resonance imaging while engaging in a picture imagination task (PIT) that included images depicting activities of daily living (ADL) and physical activity. A whole-brain exploratory analysis revealed pain catastrophizing to be correlated with neural activity in brain regions associated with aspects of emotional perception and processing, anticipation of pain, memory, attention, and visuospatial function when imagining completing ADLs and physical activity. The findings of this study suggest that individuals with ACLR who exhibit greater pain catastrophizing may experience altered brain activity when engaging in ADLs and physical activity, however these results should be interpreted with caution given there were no significant correlations present after correcting for multiple comparisons (p>0.10). In the third study examining the influence of pain catastrophizing on changes in P-MC and jump-landing biomechanics in a setting with distractions that mimic a sport environment, 23 individuals with ACLR completed the PCS, a lower extremity P-MC task, and a jump-landing task in the presence of sport-specific visual and auditory stimuli (distraction condition) and without the sport-specific visual and auditory stimuli (control condition). Differences in lower extremity P-MC and peak vertical ground reaction force (vGRF) symmetry between the distraction and control condition were calculated and separate multiple linear regression analyses indicated that PCS scores were not significantly associated with the change in ACLR limb P-MC (β=0.001, p=0.477), contralateral limb P-MC (β=0.001, p=0.438), or peak vGRF symmetry (β=-0.117, p=0.855) between conditions. These study findings suggest that pain catastrophizing may not be a critical psychological factor impacting perceptual-motor or biomechanical injury-related outcomes in sport-like settings in individuals with ACLR.
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