Tonnes of wheelchair-bound travelers of all ages fly longhauls and short all over the world each day in economy. Just inform the airline, and they will assign you an economy seat that's easily accessible, and they will assist you into and out of your economy seat.

I'm sorry to hear about your injury and surgery. You should ask your doctor if there are any precautions you should take during the flight to minimize the risk of post-surgical complications associated with flying.

I flew trans-Con (6 hours) about 4 days after some laparascopic abdominal surgery last year. My doctor indicated that there was a somewhat higher risk of developing a blood clot and he had me take a baby aspirin (thins the blood) just before take-off. He also recommended that I get up and move around a little during flight. That's harder for you, of course, but there are some movements you can do in-flight without getting out of your seat. And I'm not sure, but it might be appropriate to wear compression stockings or socks.

And as for the upgrade, you should ask on check-in what the cost might be to upgrade the final leg of your flight to Premium Economy. Sometimes the prices are ridiculously expensive, but sometimes an upgrade is available for as little as a few hundred dollars. If a few hundred dollars is within your (or your parents') budget, you could also ask the Cabin Service Director on board if such an upgrade could be purchased, once you get on the flight. Again, it might not be available, but it's worth a try.

Presumably you have medical clearance to fly after the recent surgery and that BA are aware.

Any chance you have travel insurance, that would pick up the fees for changes to your flights? Does your regular health insurance cover you out of country? Or if you paid for your flight with a cc, does your cc give you travel insurance.

Good advise Johnnyo!!! And V.S. Check his suggestions out get to BA ASAP and hope for the best.
They are a pretty good airline for being aware of helping out in emergencies and I would call this an emer.

What kind of knee surgery did you have-an arthroscope;ACL surgery;total knee replacement?

As someone who has had her knee scoped and even a double knee replacement six months ago besides being a flight attendant, I would definitely be asking if it is safe for you to fly that long?You really have to be careful and usually on something that happens randomly like this, the airline will allow you to push it back with certification a few days and perhaps a $150 change fee which I would highly recommend?
If you can change your seat,try to get a bulkhead where you could put your carry on after takeoff to elevate your leg.

Can you get a pair of compression hose-either pantyhose of over the knee as I have a strong feeling that your leg is really going to swell up.I have to wear compression hose for the next few years flying whether I am working the flight or sitting according to my surgeon.

Try and get some ziplocks so you can ask the flight attendants for ice to keep on it during the flight as this will keep the swelling down.Definitely take aspirin every 5-6 hours for the blood clots AND constantly twist your ankles and roll your feet while sitting.
Flights seem to be full on all of my international flights these days and you are traveling on a Friday which is always packed but perhaps you can be put closer to a lav or somewhere where you can elevate it.I wish you luck!

Take the blood clot thing VERY seriously!!!! VERY!!!

Talk to your doctor!!!

Yes, do take the possibility of blood clots and other complications very seriously! I have a friend who flew under similar circumstances. Even with aspirin and compression stockings, she still developed serious problems. Her leg ballooned to triple its size during the trip. She also had an embolism in one lung. She ended up in the hospital for many weeks after her arrival home, culminating in losing her leg from mid-thigh.

If at all possible get an aisle seat with your affected knee on the aisle - that way you can move/exercise it during the flight.

Donot wear compression stockings, take aspirin or anything similar without checking with a health care professional - not those here.

And even an MD letter is not going to get you an upgrade - you or I could create a nice one on fake letterhead in about a minute.

Any feedback on your flight?

1) compressive stockings
2) aspirin
3) move around constantly! don't sit on your chair for long periods of time so you don't end up with a venous clot. stretch!

I can't imagine flying after knee-replacement surgery for even several months. It takes intensive physical therapy to be able to bend the knee enough to sit in an airline seat.

I was restricted from flying for several weeks after surgery due to possibility of blood clots.
As far as seating, call the airline and ask for disability assistance. They will take care of you, maybe not moving you up to another class of cabin, but to a better seat in the front, more leg room if needed. All the airlines I have dealt with as far a disability seating have been very responsive and helpful. They always say to give them a call as soon as you book and don't wait until near flight time. I have a letter from the MD too.

OP is long gone. She flew November 30.

Julila...if you know OP......have her check back in and tell us how she did. It would be polite!

Leanna - no, I don't know the OP. Her original comment about the timing of her flight, and the fact that it appears she joined to post her question and hasn't been back since, led me to believe she's long gone.