Final answer:
The most likely condition a teenager with acute hip pain, difficulty walking, and posterior displacement of the femoral epiphysis is suffering from is slipped capital femoral epiphysis (SCFE). This is typically confirmed by X-ray and treated surgically.
Step-by-step explanation:
If a teenager presents with acute hip pain, difficulty walking, and posterior displacement of the femoral epiphysis, the most likely condition is slipped capital femoral epiphysis (SCFE). In SCFE, the head of the femur, also known as the epiphysis, slips at the growth plate (physis), which causes hip pain and a limp. This condition is more common in adolescents, particularly those who are overweight or during growth spurts. The diagnosis can be confirmed with imaging, such as an X-ray, and treatment typically includes surgical intervention to stabilize the femur and prevent further slipping.
It is noteworthy that SCFE is distinct from other hip disorders like Legg-Calvé-Perthes disease, which involves avascular necrosis of the femoral head, or Developmental dysplasia of the hip (DDH), which is commonly identified in infants and children and involves a malformation of the hip joint.
Hip osteoarthritis, on the other hand, is generally a condition affecting older individuals and is unlikely in a teenager without underlying abnormal conditions. The condition SCFE, unlike osteoarthritis, specifically involves the displacement of the epiphysis during the youth's growth period and requires prompt attention to prevent long-term hip dysfunction or further complications.