My recent experience has been a diversion after a path through both of the standard routes already mentioned prompted by a car accident a year ago tomorrow. (Wow, how time flies whether or not you're having fun!)
My first visit was to my Primary Care Physician - a regular doctor. He referred me to a physical therapy group who managed to help me with some movement and some very short-lived pain relief (until I left their office basically).
My first doctor then referred me to get an MRI which I did and an x-ray and then on to a neurosurgeon. Thankfully, the neurosurgeon said he didn't see a need for surgery nor did I have bone damage or nerve damage but all soft tissue which impinged nerves at times. He then referred me to a physiatrist - a doctor specializing in Physical Medicine and Rehabilitation (see http://www.aapmr.org/condtreat/what.htm
for more info).
She assessed my situation and was able to refer me to a rolfer (deep tissue work on the facia lining each muscle that acts as a tension maintainer for your upward stature, according to the info) and to Pilates for retraining muscles that forgot what they were there to do and generally strengthening me to hold myself upright.
I think the key person in the chain was the Physiatrist because they want you to regain your abilities and they seek out solutions of a wide variety to get you to that point. She could have sent me to a surgeon just as easily and willingly as she could send me to a chiropractor, rolfer or other alternative medicine provider.