Answer
-neuro (diffuse motor/sensory loss, progressive neuro deficits, cauda equina syndrome)
-infection (fever, IV drug use, immune suppressed)
-fracture (trauma, osteoporosis risk/fragility fracture)
-tumour (hx of cancer, unexplained wt loss, sig unexpected night pain, severe fatigue)
-inflammation (chr low back pain >3mo, age of onset <45, morning stiffness >30min, improves w/ exercise, disproportionate night pain)