Suppose you have trouble standing for long periods due to joint issues. Can you still be a surgeon? Is it possible to perform surgery while seated if necessary? Or should you look into a another speciality?
How badly do you want to be a surgeon? Enough to stand for long periods of time despite the discomfort? Or a lot, but not that much?
It's a question you'll have to answer for yourself. Just know that:
1. there will be long operations where sitting is not a reasonable option
2. long operations are more prevalent in some specialties than others (ortho, neuro at some places, and plastics reconstructive cases come to mind)
3. there are numerous shorter and mid-length operations, which can become very long if things go wrong, where sitting is not a reasonable option (most of general and CV surgery, endovascular cases, neuro/ortho spine)
4. for those operations where it is a reasonable option (anything involving the head or extremities), you will not be the one to decide whether you sit or stand until you reach the final year or so of your training
5. requiring people above you to adjust to your need/desire to sit will likely be accommodated if required medically, but will also likely be a Pyrrhic victory for you.
If you can get through training while handling the above obstacles (i.e. avoid entirely, circumvent or suck it up, as indicated), there's no reason you can't be a surgeon.