RED FLAG FRIDAY: Backpain

Although the vast majority of acute low back pain is benign, here are some "red flags" that I learned long ago to screen for:

1. FEVER—Consider infectious etiologies. After a spinal procedure such as epidural, consider spinal abscess. Also consider pylonephritis and pneumonia if pain is higher. I suppose rheumatic etiologies should be entertained (but patient should have other symptoms as well). 
2. PREVIOUS HISTORY OF CANCER—consider metastatic disease.
3. PARANEOPLASTIC SYMPTOMS—such as weight loss, night sweats, fever, etc. Also consider metastatic disease or even multiple myeloma.
4. FALL or TRAUMA or RISK OF OSTEOPOROSIS—consider fracture. 
5. CAUDA EQUINA SYMPTOMS—never seen a case in the last 15 years in medicine. And these patients would unlikely present to my office. The ER seems way more likely. But I suppose like all things, it's good to keep in mind.
6. PULSATILE MASS ON ABDOMINAL EXAM—consider abdominal aortic aneurysm. Again, I have never seen a case of this present as isolated low back pain. But I suppose someone has. 

I'm sure that there are other "red flags" for back pain. These are just the ones that come to mind off the top of my head. Does anyone else have other "red flags" to add?