Knowledge about the impact of joint impairment on functional ability is needed in planning care and setting treatment goals in children with juvenile idiopathic arthritis (JIA). We investigated the relationship between joint impairments and upper and lower limb function.
Twenty-one children with systemic JIA with an average age of 9.2 years and a mean disease duration of 4.8 years participated in this study. Joint impairments were assessed by the following variables: joint counts on swollen (JCS) and tender (JCT) joints and the loss of joint motion as determined by the Joint Alignment and Motion scale (JAM). Functional performance and functional ability were determined by the Juvenile Arthritis Functional Assessment Scale (JAFAS) and Childhood Health Assessment Questionnaire (CHAQ), respectively. The relationship between impairments and functional disabilities was studied at the level of (1) the complete instruments, (2) upper and lower limb function separately, and (3) the individual joints and items.
Regarding complete instruments, the Spearman rank correlation between functional disabilities and loss of joint motion was moderate to good (JAM/CHAQ rs = 0.66, JAM/JAFAS rs = 0.77). A fair correlation was found between functional disabilities and the joint count on swollen joints (JCS/CHAQ rs = 0.45, JCS/JAFAS rs = 0.52), but no significant relationship was found with the number of tender joints (JCT/CHAQ rs = 0.02, p > 0.05, and JCT/JAFAS rs = 0.14, p > 0.05). At the extremity level (upper and lower limb function), the relationship between functional disabilities and the loss of joint motion appeared to be stronger in the leg than in the arm. At the level of the individual joints and questionnaire items, loss of joint motion in hip or shoulder joint appeared to be the most important factor in predicting limitation in leg or arm function.
Our study shows that with respect to joint impairments, loss of joint motion is the strongest indicator of functional disability in children with systemic JIA. Loss of joint motion has a greater effect on lower limb function.