What Causes Lower Back Pain Radiating To The Buttocks, Legs And Feet?
This is classic lumbar disk disease.
Detailed Answer:
without an exam, I can only give general information and....that's what you're asking!
Symptoms
SYMPTOMS OF HERNIATED LUMBAR DISK
Severe low back pain
Pain radiating to the buttocks, legs, and feet
Pain made worse with coughing, straining, or laughing
Tingling or numbness in legs or feet
Muscle weakness or atrophy in later stages
Muscle spasm
http://www.methodistsports.com/specialties/spine/education/conditions/herniated-nucleus-pulposus-slipped-disk/
The nerve is irritated; the pain feels like it is running in the direction of the nerve.
Key points are that movements that yank on the nerve (like pulling a fishing rod) trigger the pain (extending out the leg straight). Furthermore the pain has a shooting quality. Sometimes there can be signs of nerve probelms in which case surgery might be indicated.
A magnetic resonance scan (MRI) will show the disk problem.
In theory it can be other nerve problems like lyme, multiple sclerosis, or syphillis, but these combined are not even in the same decimal place of frequency as lumbar disk (which occurs in about 10% of people).