A 7-year-old boy is brought to the orthopedic outpatient clinic by his parents due to a progressive limp and intermittent right knee discomfort over the past six months, which recently escalated to an acute inability to bear weight after a minor fall. His parents initially attributed his mild pain to a minor tripping incident during recess, but it has steadily worsened over time. He has no significant past medical history and does not currently take any medications. His height is in the 75th percentile and his weight is in the 25th percentile for his age. His vital signs are stable: temperature 37.0°C, blood pressure 100/70 mmHg, pulse 90/min, and respirations 20/min. On physical examination, the boy exhibits an antalgic gait with reduced stance phase on the right lower extremity. While there is no obvious swelling or erythema, passive range of motion of the right hip reveals markedly limited internal rotation and abduction. The left hip and knee examinations are unremarkable. Given the clinical presentation, which of the following represents the most likely diagnosis and appropriate initial management strategy for this patient?