Altered movement patterns and deviating muscular activity in individuals with anterior cruciate ligament injury

Sammanfattning: The purpose of this thesis was to increase the understanding of altered movement patterns in individuals with anterior cruciate ligament (ACL) injury in order to improve ACL rehabilitation, and to develop an observational instrument termed Test for Substitution Patterns (TSP) for standardized, quantifiable scoring of altered movement patterns in legs and trunk. In all, 142 participants, 93 with ACL-rupture (37 women) and 49 uninjured participants were investigated. The TSP was evaluated in a blinded setup and correlated to self-reported outcome instruments, hop tests, and strength tests. Surface electromyography was synchronised with electrogoniometers and video-recordings and recorded bilaterally in hip, thigh, and shank muscles while the individuals performed TSP movements and a transfer movement from double- to single-leg stances with their eyes closed. Altered movement patterns were more frequent (higher TSP score) on the injured side compared to uninjured side and compared to uninjured participants. Inter-rater and intra-rater reproducibility of the TSP were good at group level, and TSP scores correlated to self-reported outcome instruments and hop tests, but not to muscle strength. Lower muscular activity in specific muscles and changes in antagonistic activity in quadriceps/hamstrings within injured side were observed during single- and double-leg squats (SLS, DLS, included in the TSP). On injured side, the activity at movement onset in shank muscles during the transfer movement and muscle peak amplitude in antigravity muscles deviated from uninjured side. Specific altered movement patterns correlated with specific deviations in muscular activity during SLS, and low muscle activity in specific muscles at movement onset during the transfer movement correlated to high TSP score. Based on these findings, it is concluded that altered movement patterns are more frequent in individuals with ACL injury and can be quantitatively and reproducibly scored with the TSP. Deviations found in muscle activity patterns indicate altered strategies in sensorimotor control that might contribute to altered movement patterns. It is recommended that altered movement patterns and associated deviating muscular activity be considered during ACL rehabilitation.