Bone pain and malignancy red flags — branching viva

Outpatient clinic: a six-year-old boy with three weeks of deep right thigh pain that now wakes him from sleep, pallor, tiredness, and a few bruises, with non-articular tenderness over the distal femur. The examiner asks: what is the clinical task, what is the cardinal red flag, and what two tests do you order today — then branches to the four-year-old labelled as juvenile idiopathic arthritis who turns out to have leukaemia, to the adolescent with a destructive distal femoral lesion and a planned peripheral biopsy, and finally to the child with back pain and a neurological deficit.