**Core Concept**
Myositis ossificans is a condition characterized by heterotopic ossification within skeletal muscle, often occurring as a result of trauma. It involves the abnormal formation of bone tissue within the muscle, leading to restricted movement and potential complications.

**Why the Correct Answer is Right**
Myositis ossificans is indeed more common in children and adolescents, particularly after trauma. This is because the growth plates in children are more responsive to injury, leading to increased inflammation and subsequent heterotopic ossification. The condition is often seen in adolescents and young adults, making option C incorrect as it suggests that the complication is less likely in children.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is correct as myositis ossificans is indeed a post-traumatic ossification, occurring as a result of injury to the muscle or surrounding bone.

**Option B:** This option is also correct as myositis ossificans can follow either a posterior dislocation or a supracondylar fracture of the elbow joint. These types of injuries can lead to significant trauma and inflammation, resulting in heterotopic ossification.

**Option D:** While skiagraphy (radiography) can be used to diagnose myositis ossificans, it is not always a certain method, particularly in the early stages of the condition. Other imaging modalities, such as CT or MRI, may be used to confirm the diagnosis.

**Clinical Pearl / High-Yield Fact**
Myositis ossificans can be a significant cause of morbidity after trauma, particularly in children and adolescents. Early recognition and treatment are crucial to prevent long-term complications and restricted movement.

**Correct Answer Line**
✓ Correct Answer: C. The complication is less likely in children