SI-Joint pain

  Last summer I was involved in a car accident that left me with pain in my left lower back which shot down my left leg to the toes.  With this pain was numbness in my back and leg.  I am a 16 yr. old male with no prior back problems.  My MRI and bone scan were both negative.  My neurologist told me that I had a SI-Joint problem.  I have been on Voltaren and oral cortisone for the pain but they don't work.  I was wondering what exactly a SI-joint problem is and how I can how I can fix this problem.  I will try anything including surgery if possible.  I have not been given any epidurals because my neurologist doesn't believe in giving them to growing children.  Thank you for your time.
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An S-I joint problem is any problem affecting the SACRI-ILIAC joint,
which is the joint at the bottom of the spinal column where the sacral vertebrae make a connection with the bones of the pelvis.
the problem can be anything from direct injury like a fracture , to inflammation, infection or arthritis.
The fact that the pain is shooting down you leg suggests that the sciatic nerve which in this are may be affected also.
I have not had the opportunity to examine you so I cannot say what this problem in the S-I joint is. If it is directly related to the acident the chances are it will settle spontaneously, if things do not settle I would suggest tnat you ask your parents to look for a second opinion and ask about the advisability of physical therapy in your case.