A 5 year-old female complains of right knee pain for one day that initially awoke her from sleep. The pain has increased to the point where she will now no longer walk. There is no history of trauma or recent vigorous activity. She denies any fever, weight loss, or night sweats. She has a good appetite with no vomiting or diarrhea. She had transient right wrist pain five days ago.

She has no chronic medical problems, but she had strep throat one month ago that was treated with oral penicillin.

She takes no medicines and has no allergies.

Appearance:	VS Temp 37.5C, BP 110/60, HR 117, RR 20, wt 18.5kg. She is a thin apprehensive child, lying still on the stretcher.
HEENT:	NC/AT clear throat, some shoddy cervical lymphadenopathy.
Lungs:	clear bilaterally
Heart:	regular rate, no murmurs
Abdomen:	soft and benign, no splenomegaly
Extremities:	No rashes or swelling, 2+ pulses, full motion of all extremities except the right leg. Right foot is normal, the knee has no swelling or tenderness, but has pain with lateral stress. The hip is maintained in a flexed, externally rotated, abducted position. She has extreme pain with any motion of the hip.
Neuro:	normal motor and sensory exam.