I had a strange tension string going up my left leg and into my lower back a few years ago. A doctor told me it might be MS, or ALS. Wanted to do a $1,000 MRI. Scared the crap out of me.
A friend at college told me she had similar pain and that she visited a chiropractor and discovered it was a pinched nerve.
I went to a chiropractor who asked when the pain started, where it was, etc., and fixed it in two visits, saving me not only what would probably have amounted to a ton of medical bills I couldn't have paid, but severe and undue emotional distress. (My Grandpa had - and died of - ALS. I knew I didn't want it.)
More recently, after I'd been sitting lopsided (my fault) at a computer for months, my lower back started hurting. It got so bad that when Ian and I went for a walk one day, it suddenly went ZING! and I couldn't step onto or off of a curb without having to go really, really slow.
A chiropractor fixed that, too.