Page 63 - Demo

ACL reconstruction is not the only factor controlling tibial rotation613ACL-reconstructed knees showed more maximum knee flexion (60.7° vs. 53.0°, p=0.03) and less maximum knee extension (22.8° vs. 19.4°, p=0.03) during the SLHD compared to the ACL-deficient knees. During level walking ACL-reconstructed knees showed less maximum knee flexion than contralateral ACL-intact knees (41.1° vs. 43.6°, p=0.04). During the SLHD the knee flexion moment was 5-6 times higher compared to level walking and 3 times higher compared to the side jump. There was no significant difference in the generated knee flexion moment between the injured and contralateral intact knees. See supplemental material Appendix A.Discussion The main finding of our study was that, when measuring rTR in patients with a subacute ACL tear, a decrease in rTR compared to the contralateral knee was observed. Furthermore, one year after ACLR the rTR remained less than the contralateral knee. A combination of altered muscular contraction patterns and landing strategies may be responsible for these findings, rather than the result of the ACLR.We observed a greater rTR during high-demand activities than during lowdemand activities. During the hop tests the knees were exposed to a knee flexion moment six times higher than during level walking (Appendix A). The hop tests have thus been a way of presenting a biomechanical challenge as well as a psychological one, in which fear of new injury may also have played an important role. Psychological factors like kinesiophobia, selfefficacy and fear of re-injury have been determined as important in ACL rehabilitation.2 By asking subjects to perform a complex high-demand task, the effects of potentially deployed compensatory mechanisms become measurable. Hypothetically, a compensatory mechanism including altered muscular contraction may explain our findings, both before and after surgery. The exact mechanism of compensation cannot be determined based on our results, but as increased hamstring muscle activity can reduce anterior tibial translation39, and increased activity of the m. biceps Mark Zee.indd 61 03-01-2024 08:56