Background/Purpose: Though foot involvement is common in juvenile idiopathic arthritis (JIA), it is often neglected by patients and physicians alike. The involvement could occur due to arthritis, enthesitis or tenosynovitis. Tarsitis is thought to be a harbinger for spondyloarthropathy. Thus this study was done to assess clinical and radiological involvement of feet as well as its impact on function in children with JIA-Enthesitis related arthritis (ERA).

Methods: We enrolled consecutive patients newly diagnosed with JIA ERA of age less then 18 years and disease duration less than 5 years seen during 2015. All patients underwent clinical examination of the feet and answered the Juvenile arthritis foot index (JAFI) questionnaire to assess functional impact. Radiological assessment included plain X-rays of the feet, US of the joints and entheses and MRI scan of one foot. HLAB27 was done by PCR.

Results: Fifty-five patients, with a median age of 14 years and duration of disease 1.9 years were included in the study. Eighty percent (37/46) were HLAB27 positive and 18 (32.7%) had radiographic sacroiliitis. Forty six (83.6%) patients had a history of foot pain while 36 had abnormal clinical exam: 15 had ankle, 8 had subtalar 24 had midfoot and 10 had forefoot joint involvement. Tendoachilles enthesitis was present in 21 whereas plantar fasciitis was seen in 7 patients. The median JAFI score was 4 (0-11) and the score correlated with history of foot pain (r=0.66; p<0.01) and foot swelling (r=0.58; p<0.01). On plain X-ray (N=40) 3 had midfoot joint space reduction and 3 had midfoot joint fusion. On US (N=55), 16 had ankle, 8 had subtalar and 19 patients had midfoot arthritis with the talonavicular (TN) joint being the most commonly involved. 27 had US active tendoachilles enthesitis and 11 had plantar fasciitis. On MRI (N=50) tarsitis was seen in 27 patients and TN was the most commonly involved joint. Bone marrow edema was seen in 33 patients with the calcaneum being the most commonly affected bone. Midfoot enthesitis was found in 14 patients and tenosynovitis in 17 patients. Clinical and US had 82% concordance at midfoot and 90% at tibiotalar joint. MRI had lower concordance rates (74% with clinical exam and 72% with ultrasound at midfoot) as it picked up additional findings in 12 patients.

Conclusion: Foot joints and entheses are involved in a substantial proportion of patients with JIA ERA patients and lead to functional disability. Early recognition and treatment may decrease damage.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/foot-involvement-in-enthesitis-related-arthritis-subtype-of-juvenile-idiopathic-arthritis-clinical-radiological-and-functional-assessment/