Final answer:
An immature child with tenderness over the distal physis and a negative X-ray likely has a Salter-Harris I fracture, which involves separation at the growth plate and may not appear on initial X-rays.
Step-by-step explanation:
If an immature child presents with point tenderness over the distal physis of the wrist or ankle, with a negative X-ray for fractures, it most likely indicates a Salter-Harris I fracture. This type of fracture involves a separation of the physis or growth plate but does not include a break of the actual bone, which is why it may not be visible on an initial X-ray.
The Salter-Harris classification system categorizes fractures involving the growth plate, which only occur in pediatric patients. A Salter-Harris I fracture, while not visible on X-ray initially, may still cause significant tenderness at the growth plate location and swelling, necessitating a clinical diagnosis and potential follow-up imaging or other diagnostic measures.