>
> does anyone practise karate that has or has had back pain?
>
Yep.
I've had some severe backpain in the past. I used to train with a
physician who specializes in back problems. He assured me karate was
quite allright. Obviously depending a bit on your modus of training
and the specific problems you have.
And indeed it has been my experience that karate alleviates my
backpain. My wife has a back which is much worse than mine. She is a
long time karateka as well and wouldn't be able to do without training.
Mine and my wife's problem is shared by many people: sometimes certain
parts of the whole complex mechanical system that makes up your back
are slightly offset. If that is the case (which it is with most
patients) you backmuscles will tighten up to compensate and your back
will become stiff and painful. Training will help you to loosen up the
mechanics and will perhaps help some parts to slip into place again.

But I'm not a physician myself so don't take my words as a
professional advice. It's just my experience...

Igor Asselbergs
Amsterdam