Abstract
PurposeThere is sparse evidence for return to sport criteria after knee injury. Functional performance deficits, particularly in fatigued muscular condition, should be verified prior to the attempt to return to high-risk pivoting sports. The purpose of this study was to generate reference values for the limb symmetry index (LSI) of healthy subjects in fatigued and non-fatigued muscular condition in a newly designed test battery.MethodsForty-two healthy subjects [22 females, 20 males; mean (SD) age 30.4 (6.6) years] were evaluated using a test battery consisting of an isometric strength test, a series of five single-leg hop tests and an integrated fatigue protocol. Subjective physical activity was assessed with the Tegner Activity Scale (TAS). The cut-off values for healthy subjects were calculated considering the fifth percentile as the minimum reference value for the LSI and single-leg hop distance.ResultsThe mean (SD) overall LSI was 98.8% (4.6). No significant gender or age specific differences in limb symmetry were observed. The comparison of the non-fatigued LSI with the overall LSI revealed no clinically relevant change due to muscular fatigue. Repeated measures ANOVA revealed a significant within effect on fatigue/non-fatigue condition (F(1,38) = 18.000; p < 0.001, η2 = 0.321) on absolute single-leg hop distance. Moreover, a significant between effect on the TAS-parameter (F(1,38) = 5.928; p = 0.020, η2 = 0.135 between: TAS ≤ 5/TAS > 5) and on gender (F(1,38) = 23.956; p < 0.001, η2 = 0.387) could be detected.ConclusionsThe absolute jumping distance in the single-leg hop for distance was significantly reduced due to fatigue. No clinically relevant effect of muscular fatigue was observed on limb symmetry in our study sample. Gender and physical activity are important factors to be considered when interpreting reference values.
Highlights
Lesions of the anterior cruciate ligament (ACL) are the most common ligamentous injuries in the young and athletic population
No clinically relevant effect of muscular fatigue was observed on limb symmetry in our study sample
A recent systematic review and meta-analysis demonstrated that younger age and a return to high level of activity are salient factors associated with secondary ACL injury [7]
Summary
Lesions of the anterior cruciate ligament (ACL) are the most common ligamentous injuries in the young and athletic population. Problematic is the high ACL re-rupture rate. Up to 30% of young active patients who undergo ACL reconstruction suffer a second ACL rupture in the first 2 years after surgery in either the ipsilateral or contralateral knee [3,4,5,6,7]. Paterno et al reported a six times greater overall incidence rate of a second ACL injury within 24 months after reconstruction compared to first-ever ruptures [3]. A factor that might contribute to such high ACL re-rupture rates is a premature return to sports activities [4]. In patients who fulfilled specific return-to-sport criteria, an estimated 84% decrease in knee re-injury rate has been reported [4]. It has been suggested that an objective determination of the right point in time for safe return to pivoting sports after ACL reconstruction is of utmost importance, in order to decrease the likelihood of re-injury related to premature return to sports [1, 8]
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