There are a few signs on a radiograph that can indicate if a child's long bone is actively growing:
- Growth plates - These are areas of cartilage near the ends of long bones that are responsible for lengthwise bone growth. On a radiograph, growth plates will appear as radiolucent zones near the metaphysis (widened portion) of the bone. Their presence indicates the bone is still growing.
- Metaphyseal flaring - The metaphysis is the wider portion of the long bone near the growth plate. Its shape reflects active bone growth. If the metaphysis appears frayed or irregularly widened on a radiograph, it suggests active growth.
- Epiphyseal ossification centers - The epiphysis is the rounded end of the long bone. Ossification centers will be visible radiographically when this area starts to ossify (turn to bone). Their presence and progression reflect ongoing bone maturation and growth.
- Periosteal reaction - This appears as superficial new bone formation on the outer surface of the bone. It is a sign the periosteum (outer bone lining) is activated by ongoing bone expansion from growth.
So in summary, radiographic signs of growth plates, metaphyseal changes, epiphyseal development, and periosteal reaction all suggest the long bone is immature and actively growing in a child. Their presence and appearance can give clues about the rate and stage of growth.