FIGURE 121.15 Legg–Calvé–Perthes disease of left hip Epiphysis is narrowed and radiodense A subchondral fracture is also visible Initial Assessment/H&P The onset of symptoms in LCPD is usually insidious Presentation as an acute emergency is rare Mild hip pain and limp have usually been present for weeks to months before diagnosis Pain is often referred in the distribution of the obturator nerve, including the knee, anteromedial thigh, or groin Physical findings include decreased hip abduction and internal rotation Thigh muscle atrophy, and in advanced cases, limb shortening may also be noted Management/Diagnostic Testing The sequence of radiographic changes in LCPD has been described in detail ( Fig 121.15 ) Gadolinium subtraction MRI may offer radiographic evidence of disease during the first to months of symptoms when plain radiographs are normal At diagnosis, most patients have widening of the articular cartilage with a small, dense proximal femoral epiphysis Subchondral fracture may be visible Irregularity and flattening of the epiphysis develops over time The differential diagnosis includes various bone tumors and skeletal dysplasias As the disease progresses, anterolateral subluxation may be quantitated radiographically Management of LCPD requires a pediatric orthopedist who will follow and treat the child through the various stages of the disease Prompt referral may influence long-term prognosis Older children, obese children, girls, and those