Soru

An 18-month-old girl is brought to the pediatric clinic by her parents who have noticed she has been walking with a limp for the past 8 weeks. The parents report that her limp is most noticeable when she first wakes up in the morning or after naps, but her gait appears almost normal by the afternoon. She has no history of trauma, tick bites, or recent travel. She has not had any fevers, rashes, or weight loss. Vital signs are within normal limits. On physical examination, the right knee appears moderately swollen and is slightly warm compared to the left, but there is no overlying erythema. She resists full extension of the right knee but does not cry during the examination. Laboratory studies show a normal complete blood count, an erythrocyte sedimentation rate of 12 mm/h, and a C-reactive protein level of 0.3 mg/dL (normal < 1.0 mg/dL). Antinuclear antibody (ANA) testing is positive at a titer of 1:640, while rheumatoid factor is negative. Which of the following is the most appropriate next step in the management of this patient?