Hi, not sure if you are still interested but I'll have a go anyway. Firstly, I'd definitely see my gastroenterologist/rhuematologist/GP about the pain, particularly if it is severe. Also, If you already have, I would be interested to hear what he/she said.
As you said, it is possible that the leg pain is associated with your Crohn's, which is a systemic autoimmune disease. Leg pain associated with crohn's could be due to a range of causes. Pyoderma gangrenosum and erythema nodosum are skin diseases which typically affect that legs of patients with inflammatory bowel disease, but they are typically associated with dramatic skin lesions, have you noticed any changes in the skin? Another possiblity is enteropathic arthritis, which is the name given to an arthritic disease associated with inflammatory bowel disease, particularly Crohn's. However, these tend to involve discrete joints as apposed to an entire limb, but it could be that you have arthritic affecting a hip or knee associated with pain radiating throughout the leg.
Another set of possibilities include conditions which are not associated with your Chrohn's. Sciatica is a very real possibility as it fits your symptoms and is a common disease. Apart from that, a variety of common muscle and tendon injuries can cause leg pain.
I would be interested to hear how you are now and if you have seen a physician about your pain. Hope I have helped!
