Although there are many red flags of<unk> on history and physical, meta-analysis has shown the following to be predictive of fracture or malignancy:
Pain >6wk (tumor, infection)
Age >50 or <18 (tumor, congenital anomaly)
History of trauma
History of IVDU
History of cancer
History of sciatica
Neurological complaints (paresthesias, anesthesia, weakness)
Urinary retention
Incontinence of bowel/bladder
Night pain
Unremitting pain, even when supine
Fever, chills, night sweats
Anticoagulants/coagulopathy
Fever
Patient writhing in pain
Anal sphincter laxity
Perianal/perineal sensory loss (Saddle Anesthesia)
Palpable bladder post voiding or abnormal post void residual
Point vertebral tenderness
Neurological deficits
Positive straight leg raise
Back pain 
Lower back pain
Pelvic pain
Hip pain 
Hip pain
Abdominal pain 
Abdominal pain
Chest pain 