**Core Concept**
Perthes disease, also known as Legg-Calve-Perthes disease, is a childhood hip disorder characterized by transient, idiopathic ischemia of the femoral head, leading to its necrosis and fragmentation. This condition primarily affects children between 4 and 10 years of age.

**Why the Correct Answer is Right**
Perthes disease is indeed an idiopathic condition, meaning its exact cause is unknown. However, it is believed to be related to the interruption of blood supply to the femoral head, which can be due to various factors such as a femoral head deformity, trauma, or genetic predisposition. The femoral head undergoes fragmentation and necrosis due to the lack of oxygen and nutrients. The affected hip joint may become stiff and painful, leading to long-term consequences if left untreated.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Perthes disease is indeed a well-documented condition affecting children, particularly in the age group of 4 to 10 years.
* **Option B:** This option is incorrect because the exact cause of Perthes disease is idiopathic, but it is believed to be related to the interruption of blood supply to the femoral head, not directly due to trauma.
* **Option C:** This option is incorrect because Perthes disease primarily affects the femoral head, leading to its necrosis and fragmentation, not the femoral neck.

**Clinical Pearl / High-Yield Fact**
Perthes disease is often associated with a higher risk of developing osteoarthritis in the affected hip joint if left untreated or inadequately managed.

**Correct Answer: C.**