Approach to a limp (pediatrics) Quiz: Ace Your Exams

A 12-year-old girl presents to the clinic with a six-week history of a limp and pain in the right groin, upper thigh, and knee. The patient was born in a breech position and recently recovered from an upper respiratory infection about two weeks ago. Family history is significant for hypothyroidism in her parent. Vital signs are normal. Body mass index (BMI) is in the 98^th percentile for her age. On physical examination, she walks with a limp and with the right foot pointed laterally and the right thigh externally rotated. There is no warmth, redness, or swelling of the knee or hip. She experiences pain when the right hip is moved, particularly during internal rotation, and there is limited internal rotation of the hip. There is no pain or limited range of motion of the right knee. Radiographs of the pelvis show widening of the physis and displacement of the right femoral head posteriorly and medially relative to the femoral neck. Which of the following factors most likely increased this patient’s risk for the underlying condition?