Effect of anticipation on knee kinematics during a stop-jump task

1 Background: The restoration of knee rotational stability after anatomical double 2 bundle anterior cruciate ligament (ACL) reconstruction has been demonstrated in 3 cadaveric model and passive stress test on human, but not yet in dynamic functional 4 biomechanical test performed by human subjects. 5 Purpose: The purpose of the current study was to prospectively investigate the range 6 of tibial rotation of ACL deficient and reconstructed knees during a pivoting task. It was 7 hypothesized that there would be a significant increase in tibial internal rotation of ACL 8 deficient knee compared to the contralateral knee, and the increased rotation would 9 be returned to normal after anatomical double bundle ACL reconstruction. 10 Study design: Cohort study 11 Methods: Ten male subjects with unilateral ACL injury performed a high demanding 12 jump-landing and pivoting task before and after ACL reconstruction with mean follow 13 up of 11 months. The range of tibial rotation of the injured, reconstructed and intact 14 knees during the pivoting movement was measured by an optical motion analysis 15 system. Paired t-tests were performed to investigate any significant difference 16 between the two limbs pre-operatively and post-operatively, and within the injured 17 limb before and after the surgical treatment. Statistical significance was set at p<0.05 18 level. 19 Results: The range of tibial rotation was higher in ACL deficient knee than the intact 20 knee pre-operatively (p<0.05). The increased rotation was reduced in the 21 reconstructed knee after ACL reconstruction when compared to the deficient knee 22 (p<0.05). There was no significant difference in the tibial rotation between the intact 23 knee and the reconstructed knee post-operatively (p>0.05). 24 Conclusion: By assessing with a dynamic functional pivoting movement, we 25 demonstrated that the anatomical double bundle ACL reconstruction successfully 26 restored knee rotational stability from an impaired level. 27