Knee Kinematics and Kinetics During a Dynamic Balance Task and Gait in Those With and Without Generalized Joint Hypermobility

Abstract

Symptomatic generalized joint hypermobility (GJH) is a life-long condition characterized by a predisposition to joint dislocations and subluxations, disturbed proprioception, chronic pain and fatigue, degenerative joint disease, and disability. Disease burden is amplified by delayed diagnosis which is, in part, due the current reliance on an invalidated diagnostic measure of symptomatic GJH, the Beighton Score. Biomechanics has the potential to improve the identification of GJH. While no patterns have emerged that appear specific to GJH in gait, stair climbing or vertical jumping, biomechanical characteristics of postural stability appear distinct in GJH. The overall purpose of this study was to test whether performance of a dynamic balance test, the modified Star Excursion Balance Test (mSEBT), on stable and unstable surfaces, distinguishes between GJH and non-GJH in age and sex matched adults. A secondary objective was to determine the associations of performance on dynamic balance tasks with (i) the current diagnostic criteria and (ii) a measure of disease impact. It was hypothesized that maximum reach distance (MRDcomp) and maximum knee flexion angle (MKAcomp) would be smaller, and centre of pressure total excursion (COPTEcomp), dynamic knee stiffness (DKS) would be greater in those with GJH versus those without GJH. It was also hypothesized that disease impact would share a stronger association with MRDcomp than the current diagnostic criteria. This cross-sectional study design compared two age (24.6 ±4.1 years) and sex (26 females, 2 males) matched, non-athlete groups with and without GJH. From the entire sample, one participant met the criteria for symptomatic GJH. Kinematic and kinetic data were captured synchronously with research-grade motion capture (Optotrak Certus, Northern Digital Inc., Waterloo, ON, CA) and an in-ground force plate (OR6-7, Advanced Mechanical Technologies Inc., Watertown, MA, USA). First, participants performed a dynamic balance task, the mSEBT, in three conditions: stable (no foam surface), unstable (foam surface) and stable and timed. Performance on the mSEBT was measured. MKAcomp and COPTEcomp were also measured during the mSEBT. Second, DKS was averaged over five gait trials at a standardized speed (1.0 m/s). A two-way mixed analysis of variance was used to model the main effects of group and condition on for MRDcomp and MKAcomp and COPTEcomp. A Mann-Whitney U test was used to compare DKS in the non-dominant leg of both groups. Two hierarchical multiple regressions were used to determine if there is an association between (i) the current diagnostic criteria and MRDcomp, (ii) disease impact and MRDcomp, with physical activity (International Physical Activity Questionnaire) as a covariate. No significant main effect was found between MRDcomp and group (p = 0.26), showing there was no difference between GJH and non-GJH groups in MRDcomp. No significant main effect was found between COPTEcomp and group (p = 0.99), showing there was no difference between GJH and non-GJH groups in COPTEcomp. No significant main effect was found in MKAcomp between groups (p = 0.45), showing there was no difference between the amount of maximum knee flexion between non-GJH and GJH groups during the mSEBT. No significant difference was found between GJH and non-GJH groups for DKS in the timed condition (p = 0.22). The regression models identified that the diagnostic criteria (Beighton Score) (R2 = 0.07; p = 0.90) and disease impact (Bristol Impact of Hypermobility Questionnaire) (R2 = 0.08; p = 0.95) were not associated with MRDcomp. The results of this study indicate performance on the mSEBT and DKS are not different in GJH than non-GJH groups in this sample of non-athlete university graduate and undergraduate students. Additionally, a measure of disease impact does not better associate with performance on the mSEBT than the current diagnostic criteria in this study’s sample. Strengths of study include using a combination of novel clinical and biomechanical methods and measures in those with GJH. Future work on the clinical use of the mSEBT and DKS may consider recruiting those with symptomatic GJH and/or older participants with GJH.