The Effects of Joint Hypermobility on Pain and Functional Biomechanics in Adolescents with Chronic Musculoskeletal Pain: Secondary Baseline Analysis from a Pilot Randomized Controlled Trial

Abstract Background : Joint hypermobility (JH) is a common clinical finding amongst hereditary connective tissue disorders that is observed in pediatric rheumatological settings, and often associated with chronic pain. JH may also contribute to deficits in physical functioning and physical activity, but previous findings have been inconsistent. It is possible that physical activity impairment in JH may be due to chronic aberrant movement patterns subsequent to increased joint laxity. Method: As part of a larger randomized pilot trial of juvenile onset fibromyalgia (JFM), asecondary analysis was conducted to explore whether adolescents with JFM and JH differed from non-JH peers in terms of pain, daily functioning, and movement biomechanics during a moderately vigorous functional task. Results : Thirteen adolescents (36.1%) from the larger sample of adolescents with JFM (N=36) met criteria for JH. Those with JH exhibited poorer overall functioning but there were no differences in pain. Those with JH exhibited decreased hip flexion and frontal plane hip moment (e.g., resistance to dynamic valgus) during the landing phase (early stance) and greater hip and knee transverse plane moments during the propulsion phase (late stance) of the drop vertical jump task (DVJ). No other differences in lower extremity biomechanics were observed between study groups. Conclusions : There were small but notable differences in biomechanics between patients with JFM who also had JH versus those without JH during a landing and jumping task (e.g., DVJ). These differences may indicate decreased joint stiffness during landing, associated with increased joint laxity and decreased joint stability, which may put them at greater risk for injury. Further study is warranted to examine whether these biomechanical differences in patients with JFM and JH affect their response to typical physical therapy or exercise recommendations.