What distinguishes transient osteoporosis of the hip from avascular necrosis in physical exams?

Transient osteoporosis of the hip is characterized by a temporary condition where the hip experiences significant bone loss and decreased density, often preceding recovery without permanent effects. One of the key distinguishing features in physical examinations is that it typically maintains a preserved range of motion. This means that although the patient may experience pain, especially with weight-bearing activities, they do not exhibit significant limitations in their overall joint mobility during the exam.

In contrast, avascular necrosis involves the death of bone tissue due to a lack of blood supply, leading to structural changes in the bone that can severely affect joint function. This condition often results in significant limitations in the range of motion, characterized by pain and stiffness, especially in hip rotation and other movements, making the differentiation crucial during a physical examination.

Therefore, the preservation of range of motion in transient osteoporosis highlights its differentiating factor from avascular necrosis, where mobility is often compromised due to more severe joint pathology.