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ObjectiveJuvenile idiopathic arthritis (JIA) affects body structure and function and physical activity outcomes. The present study was undertaken to examine differences in gait kinematics during fixed‐speed treadmill walking for youth with JIA and typically developing (TD) youth.MethodsSagittal plane gait kinematics were obtained using a 12‐camera system (Motion Analysis) for youth with JIA (n = 30) and their age and sex‐matched TD peers (n = 30). Outcomes included disease activity, pain, well‐being, and peak sagittal hip, knee, and ankle joint angles. Kinematics were analyzed for the indexed leg (IL) (i.e., the affected leg of participants with JIA) compared to the dominant leg of TD participants and for the contralateral leg (CL) (i.e., the less/not affected leg of participants with JIA) compared to the nondominant leg of TD participants. Kinematics differences were investigated using multivariate Hotelling's T2 statistic (paired samples; α = 0.05) and simultaneous 95% confidence intervals (95% CIs). Potential confounders (age, sex, body mass index) were assessed using linear mixed‐effects models with random effect for pairs.ResultsYouth with JIA had low disease activity, pain, and disability scores. Deviations in bilateral joint angles were observed (IL P = 0.015, CL P = 0.009). Youth with JIA walked with greater initial hip flexion (mean difference IL 2.8° [95% CI –0.6, 6.2]; CL 3.0° [–0.9, 6.9]) and lower knee extension (mean difference IL –2.2° [95% CI –4.4, 0.1]; CL –3.3° [–7.4, 0.8]), and lower hip extension during terminal stance (mean difference IL 3.4° [95% CI –0.3, 7.0]; CL 4.0° [1.0, 7.0]).ConclusionDespite low disease activity, youth with JIA avoided the close‐packed knee position, commonly associated with joint inflammation and pain. These findings highlight secondary consequences of JIA and inform targets for physical therapy management for youth with JIA.

Objective Juvenile idiopathic arthritis (JIA) is associated with altered body structure and function outcomes that may expose youth with JIA to a greater risk of secondary joint injury. This study aimed to examine differences in vertical drop jump (VDJ) biomechanics for youth with JIA and healthy youth (control group). Methods The present study was a matched pair cohort study. Youth with JIA (n = 30) and their age‐ and sex‐matched control peers participated in this ethics‐approved study. Lower‐extremity biomechanics information was obtained using a motion analysis system (Motion Analysis) and 2 force plates (AMTI). Biomechanics outcomes included hip, knee, and ankle joint angles, ground reaction forces (GRF), and VDJ phase durations. Other outcomes included disease activity, physical disability, and sports participation. Matched pairs data (JIA–control) were analyzed using a multivariate random coefficient model (version 3.5.0, R Core Team; joint angles, potential confounders) and paired samples t‐tests with Bonferroni correction (α = 0.0125; GRF, VDJ phase durations). Results Youth with JIA had low disease activity, pain, and disability scores. Youth with JIA maintained a more erect posture at the hip (β = –4.0°, P = 0.004), knee (β = 7.5°, P = 0.004) and ankle (β = –2.6°, P = 0.001). GRF and phase durations outcomes did not meet criteria for significant differences. Knee extension increased with participant age (β = –1.0°, P = 0.002), while female participants displayed greater hip flexion (β = –6.6°, P = 0.001) and less ankle dorsiflexion (β = 2.3°, P = 0.006). Conclusion This study provides evidence for a stiff knee landing strategy by youth with JIA. These findings inform targets for physical therapy management to mitigate the risks of a secondary joint injury in sports participation.

Objective. Juvenile idiopathic arthritis (JIA) affects body structure and function outcomes that may increase the risk of acute joint injury. The purpose of this study was to examine single leg squat (SLS) biomechanics for youth with JIA and their healthy peers. The study design was a matched pair cohort study.Methods. Sixty-five youth (JIA n = 30; control n = 35) participated in this ethics-approved study. Participants performed 3 sets of 5 consecutive SLS tasks. Disease activity and functional status were assessed using the Juvenile Arthritis Disease Activity Score and Child Health Assessment Questionnaire. Indexed (most-affected leg [JIA]; dominant leg [control]) and contralateral extremity biomechanics were obtained using a 12-camera system. Outcomes included hip flexion/extension (FE), adduction/abduction (AA), and internal/external (IE) rotation range of motion (ROM). Data were analyzed using a multivariate random coefficient model in R (α⍺ = 0.05).Results. A total of 29 matched pairs were analyzed. Youth with JIA had low disease activity and performed the SLS with a more internally rotated hip (indexed leg P = 0.023, β = -1.9°). Female participants displayed greater hip FE (indexed leg P = 0.015, β = -4.3°; contralateral leg P = 0.005, β = -4.8°) and IE ROM (indexed leg P = 0.021, β = -2.1°) than male participants. Associations were observed for body mass index and hip IE ROM (contralateral leg P = 0.001, β = -0.4°), knee flexion angle, and hip FE ROM (indexed leg P = 0.001, β = 0.4°; contralateral leg P = 0.001, β = 0.5°) and AA (indexed leg P = 0.010, β = 0.1°; contralateral leg P = 0.002, β = 0.2°).Conclusion. This study identified functional alterations for an SLS in youth with JIA. These findings support the use of physical therapy as part of a multidisciplinary management approach, to restore normal hip posture and movement.