joint and muscle pain?

I have no idea if this is related to UC, remicade, flying, or just another ailment to add to the list...

The events are Wednesday I had a 6 hr flight, Thursday I had my 6th remicade infusion and Sunday I had another 6 hr flight. It started out as minor muscle pain in my calf, but I can't remember if it started after the flight on Wednesday or after the remicade on Thursday. I haven't done any strenuous exercise or caused injury to my leg. It didn't bother me much other than give the feeling that I had really strained the muscles in my calf as if I had been running a lot. Today the pain has moved from my calf to my knee joint and this evening it has become very painful. It hurts to walk on it. It hurts when I am just sitting too. It feels like someone is trying to pry my leg apart at the knee joint. There is no swelling, but when I squeeze my calf close to my knee the pain increases.

I will go to the doctor if it gets worse, but I was hoping for some thoughts. I am from Canada, but currently in the US so going to see the doctor would not be my first choice. Things that have crossed my mind as I try to self diagnose are blood clot from flying, joint pain related to UC or some side effect of Remicade.

Has anybody had experience with muscle/joint pain like this?

I ended up going to emergency last night. The doc said it is not likely a blood clot because there is no hot spot or swelling. The pain peaked in my knee and lower leg last night. I took a motrin and it helped.

I still had a bit of pain today, but nothing like last night. Seems to be going away. I don't have a clue what it was and I really hope it doesn't come back.