It's not unusual... I experienced something similar a year or two ago. My lower back really hurt and I couldn't straighten and lift my legs, like on the quad extension machine at the gym. I believe at least one other member here has mentioned having the same problem. I went to a chiropractor for a few sessions and got quite a bit of relief. His thought was the inflammation in the abdomen from a UC flare can also cause related inflammation in the SI joint of the lower spine.http://en.wikipedia.org/wiki/Sacroiliac_joint
Diagnosed with ulcerative colitis spring 1999
C-scope confirmed UC diagnosis 9/18/2007
No explanation for right side pain and thickening of bowel wall
Maintenance dose sulfasalazine, back on a pred taper for first flare in years
Probiotics, l-glutamine and fish oil caps. George's aloe vera juice and Mucosaheal.