Wrist and ankle MRI of patients with juvenile idiopathic arthritis: identification of unsuspected multicompartmental tenosynovitis and arthritis.

OBJECTIVE: The purpose of this study was to characterize the extent of joint and tendon involvement in patients with juvenile idiopathic arthritis referred for MRI of the wrist or ankle.
MATERIALS AND METHODS: Forty-five patients (32 female and 13 male patients; mean age, 10 years; age range, 1-19 years) with an established diagnosis of juvenile idiopathic arthritis were referred for MRI of the wrist or ankle between January 2000 and August 2012 (39 wrists and 33 ankles). All MRI examinations and clinical notes were reviewed, and joint and tendon involvement was recorded.
RESULTS: Tenosynovitis was present in 50% (36/72) of examinations. Tenosynovitis was not documented in clinical notes before MRI. When tenosynovitis was present, an average of 3.5 tendons were involved (range, 1-12 tendons). For the wrist, 59% (23/39) had tenosynovitis, and the extensor digitorum tendon (23% [9/39]) was most commonly involved. For the ankle, 39% (13/33) had tenosynovitis, and the tibialis posterior tendon (33.3% [11/33]) was most commonly involved. For the wrist, 89.7% (35/39) had active joint inflammation with an average of 3.1 joints involved (range, 0-6 joints), and the intercarpal joint was most commonly involved (69% [27/39]). For the ankle, 69.7% (23/33) had active joint inflammation, with an average of 2.4 joints involved (range, 0-5 joints), and the tibiotalar joint (52% [17/33]) was most commonly involved.
CONCLUSION: Multicompartmental tenosynovitis and arthritis involvement is common in patients with juvenile idiopathic arthritis referred for MRI of the wrist or ankle and is underappreciated on clinical examination. International League of Associations for Rheumatology subclassification and targeted intraarticular steroid injections guided by clinical examination alone may lead to undertreatment or incorrect treatment of active disease.