Do we need to reconsider knee valgus as a sole risk factor for second ACL injury? Exploratory analysis of individual Landing Error Scoring System (LESS) items with three year follow-up

BackgroundIt remains unclear which movement quality items are associated with second anterior cruciate ligament (ACL) injuries after ACL reconstruction. Hypotheses1) Movement quality measured with the Landing Error Scoring System (LESS) is not associated with second ACL injury in soccer players who returned to sports after ACL reconstruction. 2) In an exploratory analysis, soccer players with and without second ACL injuries display differences in individual LESS items. MethodsFourteen male recreational ACL-reconstructed soccer players had non-fatigued and fatigued movement quality measurement with LESS score three years ago and were now interviewed by phone about soccer participation and second ACL injuries. ResultsTwo soccer players did not return to soccer and were therefore excluded from analysis. Six of twelve (50%) included soccer players had a second ACL injury. There was no association between the non-fatigued (p=1.000) and fatigued (p=0.455) LESS score and second ACL injuries. However, when exploring individual LESS items, we found 50% of the soccer players with second ACL injury landing with little trunk and knee flexion displacement in combination with knee valgus, while none of the soccer players without second ACL injury had this combination of LESS errors. This difference was only seen in the fatigued state. ConclusionsIt might be the combination of little knee and trunk flexion displacement with knee valgus during landing which predisposes an athlete to a second ACL injury, especially in a fatigued state. Clinical relevanceWhen screening athletes after ACL reconstruction for second ACL injury risk, combining measurement of knee valgus with knee and trunk flexion displacement in a fatigued state might be give more insight into risk than using the complete LESS score or evaluating knee valgus as a sole risk factor.