Objective: To compare lower-leg strength of young girls with polyarticular juvenile idiopathic arthritis (JIA) with that of healthy, age-matched controls.
Design: Isometric and isokinetic strength tests of the plantar- and dorsiflexors. All strength measures were made at an ankle angle of 90 degrees. Isokinetic plantar- and dorsiflexor measures were made at 15 degrees/s during shortening (concentric) and lengthening (eccentric) actions.
Setting: Strength testing laboratory.
Participants: Ten prepubertal girls diagnosed with JIA and 10 healthy girls.
Interventions: Not applicable.
Main outcome measures: Isometric and isokinetic plantar- and dorsiflexor strength.
Results: Isometric plantar- and dorsiflexion torques were significantly lower (48% and 38% respectively; P<.05) for the children with JIA than for the controls. The JIA group also produced lower shortening plantarflexion torques (52%, P<.05). Lengthening plantarflexor torques did not differ significantly between the 2 groups (P<.05). Controls were stronger than the JIA group for both shortening and lengthening maximal dorsiflexor actions (P<.05). All children were 4 to 5 times stronger in plantarflexion than in dorsiflexion.
Conclusions: Girls with JIA had significantly less plantar- and dorsiflexor strength than age-matched, healthy peers. The reduced strength of children with JIA is likely to affect function in daily activities and probably contributes to reduced levels of physical activity.