A 2-year old male was playing indoors three hours ago. His mother noticed that he was not walking and he began to complain of right leg pain. There was no history of trauma. He did have a cold for the last week and had a fever. His highest temperature measured at home was 40.5 degrees. The patient was seen in his pediatrician's office earlier in the day for fever and was prescribed amoxicillin for an ear infection. The patient returned the pediatrician's office later in the afternoon because he was refusing to walk. There is no history of sore throat or rash. The patient was sent to the ED for further evaluation. His past medical history is unremarkable.

Exam: Vital signs T38.1 (tympanic), P193, R28, BP 127/85, O2sat 99%(RA), Wt13.4kg (75%ile). He is alert and is being carried by his mother. His left lower extremity is nontender with full range of motion of his left hip, knee, and ankle. His right hip, femur, knee, proximal tibia and fibula, and foot are nontender. There is normal range of motion of his right hip and knee. There is reproducible point tenderness over the right anterior ankle joint, possibly the talus. There is pain elicited with right ankle range of motion. There is no swelling, overlying skin lesion, erythema, or asymmetric warmth. Pulses are good. Toes are pink. Radiographs of his right hip, knee, leg, ankle and foot are obtained.

View ankle and foot radiographs.