This longitudinal lucency projected across the epiphysis is not a fracture (it would be a Salter-Harris III), but a cleft epiphysis. There are normal developmental variants and can be mistaken for fractures.
In this case, the clinical team were not concerned about a fracture and after discussion with orthopedics, the child was mobilized and at the returns clinical was symptom free 48 hours later. No further radiographs were taken.