I did have problems with headaches at first but they initially put me on the high dose very fast so with a very helpful rhumo nurse I stopped them then gradually built them up which helped a lot.
I'd also take them at night while building them up so the effect was less until my body got used to them.
Switching to enteric coated tablets also helped a lot.
You should have 2 weekly bloods done until you've been able to tolerate the full dose for a month so loads of opportunity to get help and advice from the nurses.
Mine feel very weak sometimes and it's just agony trying to walk but I know if I don't move I will just seize up even more. I was in bed for a week and in serious pain trying to get up and about afterwards.
Osteo really helps and mine keeps a close eye on the medical side of things too which is really helpful. The relief may only be temporary but it makes a big difference.
You could try some private tutition with a specialist in yoga or pilates for it which may help you to be able to build up strength, improve posture and balance your weight better.
If it's really affecting you, a walking aid may be a consideration.
There are forums out there which may help you, found one here...
http://www.ulcerativecolitis.org.uk/colitisfor um/index.php
You can also google inflammatory bowel arthritis for more info as it's not the usual sort and doesn't tend to cause lasting damage to the joints.
Have you had any recent XRays to check on any damage?
I'm still waiting to get back to gastro to see what they think, soon I hope as tummy has not been happy lately though things have been stressful which hasn't helped.