**Core Concept**
Acute compartment syndrome (ACS) is a condition characterized by increased pressure within a muscle compartment, leading to nerve and muscle ischemia. In children, ACS is often caused by a traumatic injury that results in swelling and increased pressure within a closed fascial space.

**Why the Correct Answer is Right**
The most common cause of ACS in children is a long bone fracture, particularly in the lower extremities. This occurs when a fracture leads to swelling and bleeding within the muscle compartment, causing increased pressure and potentially leading to nerve and muscle ischemia. The tibia is the most commonly affected bone in children, due to its location and the potential for significant swelling following a fracture.

**Why Each Wrong Option is Incorrect**
**Option A:** While overuse or repetitive strain can cause compartment syndrome, it is not the most common cause in children. Overuse injuries typically cause chronic compartment syndrome, rather than acute.
**Option B:** Burns can cause compartment syndrome, but they are not the most common cause in children. Burns typically cause a different type of injury pattern than fractures.
**Option C:** Crush injuries can cause compartment syndrome, but they are not the most common cause in children. Crush injuries are more common in adults and typically cause a different type of injury pattern than fractures.

**Clinical Pearl / High-Yield Fact**
In children, the most common presentation of compartment syndrome is pain out of proportion to the injury, particularly with passive stretching of the affected muscle group. This is often the first sign of compartment syndrome, and prompt recognition and treatment are essential to prevent long-term nerve and muscle damage.

**Correct Answer: D. Long bone fracture**