Absolutely.
Nobody ever expects (extreme case)
Itzhak Perlman to stand.
Personally, I'd be a happy audience if a flautist sat on a barstool, as many guitarists tend to do.
Now, performing while on a unicycle...
music.stackexchange.com/users/6275/Carl Witthoft
I've never seen a flutist sit, but I've also not seen very many flute soloists.
What I have seen is plenty of soloists that do sit, so you'd be in good company!
And keep in mind that cellists, pianists, harpists, tubists, etc.
sit.
Why should you feel out of place for sitting?
Do whatever helps you perform the best!
music.stackexchange.com/users/21766/Richard
Orchestral flautists sit the whole time
so it's clearly possible to play the flute to a high standard while sitting.
It's the 21st century and people are used to legislation that requires employers to make reasonable accommodations for people with disabilities.
This doesn't sound like an employment situation but the same principles and expectations apply.
There's no reason you shouldn't sit, and every reason that you should.
The audience wants to hear you at your best.
music.stackexchange.com/users/10074/David Richerby
If you were performing in an ensemble of 3 or more people - a flute quartet for example - you would not think twice would you; you would always sit.
So its not really an unusual way to perform.
And even if it were you are still free to do whatever you need to feel comfortable and perform at your best.
So go for it, and good luck with the performance
music.stackexchange.com/users/24412/JimM
It's always acceptable to be seated.
Standing is more conventional for a single soloist, but a group of performers would be seated.
The only advantage of standing would be diaphragm and breath control.
That isn't an insurmountable obstacle whilst playing.
music.stackexchange.com/users/59061/Greg
When I was playing (and I'm older than you are), allowances were always made for medical situations.
I never saw any of my fellow flutists standing and playing with crutches.
But be careful.
One of the reasons to stand includes the fact that it's simply better for breath control—and the flute uses more air than any orchestral instrument except for the tuba.
When seated, as with the rest of the orchestra, you can still fill your lungs completely with good breath control, but you have to take care to sit with good posture that facilitates breathing.
Sitting on a "bar chair" might allow you to breathe easily, but then again it might not.
And in compensating for the extra height you might put some other part of your body out of whack or off balance.
At which point I'll add that if you think you have problems now, try falling off a high chair in front of an audience!
music.stackexchange.com/users/5712/Robusto
Conventionally, soloists stand.
So what?
Do you honestly feel that any objection would be raised to one sitting for medical reasons?
Of course not!
So I guess your post is really about getting reassurance and recognition for your achievement.
No problem.
Well done!
Hope
it goes well.
Good luck!
(Will that do?
You're welcome.)
music.stackexchange.com/users/17003/Laurence Payne
I am a 60 year old flutist and I am about to perform a humble concert in my community.  I have plantar fasciitis in my left foot, and I wonder if it is acceptable for me to sit on a high chair (like bar chair height) instead of stand for my performance?  Does any one have any thoughts? Have you ever seen anything like this?
Can a flute soloist sit?
music.stackexchange.com
<performing><flute>
music.stackexchange.com/questions/82589
music.stackexchange.com/users/59051/Kristine Kirby
Orchestral flautists sit the whole time, so it's clearly possible to play the flute to a high standard while sitting. If you were performing in an ensemble of 3 or more people - a flute quartet for example - you would not think twice would you;  you would always sit. Standing is more conventional for a single soloist, but a group of performers would be seated.   . One of the reasons  to  stand includes the fact that it's simply better for breath control—and the flute uses more air than any orchestral instrument except for the tuba. When seated, as with the rest of the orchestra, you can still fill your lungs completely with good breath control, but you have to take care to sit with good posture that facilitates breathing. Standing is more conventional for a single soloist, but a group of performers would be seated.
Orchestral flautists sit the whole time. Standing is more conventional for a single soloist, but a group of performers would be seated. The flute uses more air than any orchestral instrument except for the tuba. When seated, as with the rest of the orchestra, you can still fill your lungs completely with good breath control. But you have to take care to sit with good posture that facilitates breathing.