An 8-year-old afebrile male patient is referred to the Ortho…

An 8-yeаr-оld аfebrile mаle patient is referred tо the Orthоpedic clinic because he has significant right hip and knee pain. The patient is noted to walk with a limp as he enters the office, and the patient’s mother denies any history of trauma. On physical examination, you note atrophy of the right quadriceps muscles and decreased range of motion (ROM) of the right hip, particularly with internal rotation and abduction. Leg length inequality is also observed on the right compared with the left. Frog-leg radiographs of the right hip reveal cessation of growth at the capital femoral epiphysis and a smaller femoral head epiphysis with widening of the articular space on the right side. White blood cell counts, C-reactive protein, and erythrocyte sedimentation rates are all normal. Which of the following conditions is the most likely diagnosis?