Abstract
BackgroundAltered knee muscle activity in children with asymptomatic Generalized Joint Hypermobility (GJH) is reported during isometric contraction, static and dynamic balance tasks and jumping, but has not been studied during gait. Therefore, the aim was to investigate group differences in knee muscle activity simultaneously with knee joint kinematics during treadmill walking between children with and without GJH.MethodsGirls 14–15 years of age with GJH (inclusion criteria: Beighton score ≥6 of 9 and positive hyperextension ≥10° (one/both knees)) and a matched control group without GJH (inclusion criteria: Beighton score ≤5 and no knee hyperextension ≥10° ) were recruited. In total 16 participants with GJH and 10 non-GJH participants were included in the study.Surface electromyography (sEMG) was measured from the quadriceps, hamstrings and gastrocnemius muscles of the dominant leg during treadmill walking. Maximal voluntary isometric contractions while sitting were used for normalisation of sEMG to % of Maximum Voluntary EMG (%MVE). Knee joint angles during treadmill walking were measured by electrogoniometer. Furthermore, co-contraction index (CCI) was calculated, and presented for muscle groups of hamstrings-quadriceps (HQ) and gastrocnemius-quadriceps (GQ). CCI of medial and lateral sides of the knee, including ratio of the medial and lateral CCI for HQ and GQ were calculated.ResultsNo group differences were found in demographics, muscle activation level, nor CCI and CCI ratios. However, participants with GJH displayed significantly decreased knee joint angle, mean (153º vs. 156º; p =0.03) and minimum (105º vs. 111º; p=0.01), during treadmill walking compared with controls.ConclusionMuscle activity during gait was not different between participants with GJH and non-GJH participants. However, participants with GJH displayed minor but statistically significant increased knee flexion during gait. Since the clinical consequences of increased knee joint flexion during gait are unknown, future studies should follow a larger cohort longitudinally during overground walking for development of clinical complications in this group.
Highlights
Altered knee muscle activity in children with asymptomatic Generalized Joint Hypermobility (GJH) is reported during isometric contraction, static and dynamic balance tasks and jumping, but has not been studied during gait
When GJH becomes symptomatic, pain is a key factor in both children [8,9,10], and adults [11] and the condition may in some cases be diagnosed as the more severe Hypermobility Spectrum Disorder (HSD) [12], or an inherited connective tissue disorder, like hypermobile Ehlers-Danlos Syndrome
In total, 26 children were included in the analyses, corresponding to 16 participants with GJH and 10 non-GJH participants
Summary
Altered knee muscle activity in children with asymptomatic Generalized Joint Hypermobility (GJH) is reported during isometric contraction, static and dynamic balance tasks and jumping, but has not been studied during gait. Prevalence varies across ethnic groups and is most frequent among females [2] It is classified clinically with the Beighton score [3, 4], with a cut-off point of 6/9 for Caucasian children [5, 6]. Using these cut-off points, a recent study has estimated the prevalence of GJH to represent about 3–6 % in an Australian normal population [7]. When GJH becomes symptomatic, pain is a key factor in both children [8,9,10], and adults [11] and the condition may in some cases be diagnosed as the more severe Hypermobility Spectrum Disorder (HSD) [12], or an inherited connective tissue disorder, like hypermobile Ehlers-Danlos Syndrome (hEDS)
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