Lower limb abnormalities in children with juvenile idiopathic arthritis

Juvenile Idiopathic Arthritis (JIA) is a group of diseases of childhood onset characterised primarily by arthritis persisting for at least six weeks with no known cause (Petty et al, 1998). In the U. K., there are an estimated 12,000 children with JIA (Arthritis Research Campaign, 2002). There is little literature on the effects of JIA on the foot and ankle from a podiatric perspective. The aim of the current study was to investigate lower limb abnormalities in children with JIA compared to healthy children. A cross-sectional study was conducted on 50 healthy subjects (healthy control group) and 50 subjects with JIA aged 7-16 years. The JIA subjects were divided into a group with foot and/or ankle involvement in the disease (JIA study group) and those with no foot and/or ankle involvement in the disease (JIA control group). Three assessments were performed; specific joint involvement in the foot and ankle (JIA study group only), lower limb alignment and joint motion using goniometry, and plantar pressures/vertical component of ground reaction force (GRF) using the Musgrave@ Footprint System. Data was analysed using descriptive statistics and General Linear Model (GLM), which combines Analysis of Variance (ANOVA) with linear regression. After the ankle joint (97%), the most commonly affected joints in the foot/ankle of subjects in the JIA study group were the subtalar joint (STJ), in just over half of subjects (53.1%), and the Is' Metatarsophalangeal Joint in just under half (43.7%). Bilateral involvement of the ankle and foot joints was more common than unilateral. There was evidence of a reduced range of motion in the ankle, subtalar and Is' metatarsophalangeal joints in subjects in the JIA study group compared to the JIA and healthy control groups. These joints have a significant role in locomotion; providing shock absorption, effective propulsion, and the ability to adapt to uneven terrains, therefore this finding has great implications for gait in children with JIA affecting the foot and ankle. According to GLM analysis, there was evidence that the STJ neutral position had a greater valgus orientation in the JIA study group compared to the JIA and healthy control groups (P<0.01), indicating the potential for pathological conditions resulting from over-pronation at the STJ. However, this was not found for either resting or neutral calcaneal stance positions. Children in the JIA study group had a shorter foot length than the JIA or healthy control groups (P<0.01), indicating the possible involvement of the disease process on foot growth in these children. Force-time curves in subjects with JIA were flatter in appearance compared to healthy children, in agreement with other studies in this area (Frigo et al, 1996; Brostrom et al, 2002). This finding was due in part to a significant reduction in force peak during propulsion (FPP) (P<0.001 left, P<0.05 right) and pressure at FPP (P<0.001 left, P<0.001 right) in JIA study group subjects, according to GLM analysis, indicating a less efficient propulsive action during gait. This finding may be explained by a reduced walking velocity or reduction in plantarflexion during gait in children with foot/ankle involvement in JIA. However, similar to other studies in this area (Frigo et al, 1996; Brostrom et al, 2002) analysis using GLM statistics showed no evidence (P>0.05) of a difference in temporal measures such as total contact time, time to FPP or percentage of footprint at FPP between subject groups. It is anticipated the results of this study will contribute to an increased level of knowledge of foot and gait abnormalities in children with JIA, by providing joint involvement, joint motion, GRF and plantar pressure data compared to a healthy control group. This data may then be used to assess the outcomes of podiatric management and help achieve the goals of podiatric management i. e. to control foot posture, prevent long-term deformity, maximise joint function and reduce pain. Some normative values on healthy children have also been provided, which may be informative to health care professionals involved in the care of children. Unfortunately, podiatrists may not be involved in the management of children with JIA affecting the foot or ankle until a later stage, when foot deformities have already developed and treatment is limited to palliative care. The results of this study have highlighted the deviations in foot posture and gait in children with JIA in comparison to healthy subjects of a similar age, and it is hoped that these results will emphasise the importance of podiatric input at an early stage to reduce functional limitation and improve outcome for patients with JIA affecting the foot and ankle. The use of functional foot orthoses (FFOs) to control foot posture in children with JIA is an exiting area of podiatric management. However there is no empirical evidence on which to base this practice. The current study has provided baseline data on both healthy children and those with JIA, which may be of use to future researchers in providing the evidence for the effectiveness of FFOs in the podiatric management of children with JIA.