Back pain may have various causes. Discs, muscles, facet joints or from tissues or organs far from the back.
The most important 1st step is a thorough physical exam which needs to be performed with the patient undressed.
Along with the back, the groin region and abdomen should also be examined.
MRI should be performed only if a question remains as to the cause after the physical exam or if the pain does not resolve with the proposed therapy.
If you are having loss of bowel or bladder control then you should go immediately to the ER and be evaluated for a potentially serious medical problem.
Back pain with radiation of pain below the knee might indicate nerve root compression.
Please talk to your doctor as soon as possible.
In order to answer your question adequately, I would need to know the answers to the following questions
Where is the location of the pain on the legs?
What makes the pain worse, what makes it better?
How long has the pain being bothering you?
What activities are you unable to perform as a result of having leg pain?
Have you been seen by a Medical Physician and if so what was the diagnosis?
Have you had any diagnostic testing such as MRI, EMG/NCS, studies of your blood supply to the legs?
Did you suffer a back injury which caused the pain in your legs?
Please respond to the above questions and I would be able to answer your question in a more meaningful manner.
Thank you for asking this question.
Dr. Joshi