Commercial jets are pressurized to 8,000ft elevation. This reduced cabin pressure causes all kinds of funky things to your body and especially joints. If you have preexisting body aches, arthritis, past injuries, inflammatory conditions or other auto-immune diseases it's quite possibly exacerbating an underlying condition.

As others said, talk to a doctor or two.

Nothing is wrong with you. Flying sucks.

Choose an aisle or window seat to your preference, bearing in mind that one of the solutions to body soreness when airplane traveling is standing up for 10 mins every 30-40 mins.

If you can swing it, fly first class, since the seats are wider and you can more easily shift your body weight.

E: typo

I’m about to have this issue in about 10 hours. Are you older than 30? Cuz I really started feeling the pain after 30. I recently bought an awesome inflatable pillow that keeps my head upright, so I can maybe possibly sleep instead of just fidgeting and suffering through the whole flight. I feel your pain, internet stranger.

Also, constipation. It’s so hard to shit the day after flying. Most people don’t seem to have this issue.

You might have some issues with one of your intervertebral discs. Go do a checkup just to make sure. Might catch it before it evolves into a bigger problem.

I always buy an aisle seat so I can stretch my legs and get up whenever I need.

I've also learned that most airlines (at least here in Europe) fill their seats from the front back. So if you sit near the back and keep an eye on the back row, sometimes it's completely unoccupied. In which case I move there and can practically lie down.

Are you otherwise very active on any given day when you're not on a plane? Maybe you're never sitting that still and confined for 5 hours straight and your body just isn't used to it? Are you tall? I can see where it would totally suck to be tall and fly for any amount of time, really. The only time I'm ever thankful to be 5'3" is when I'm flying and can have a bag under the seat in front of me and still stretch out my legs and cross my legs if I want to.

Your urine should be a light yellow color. (Note: recent food/beverage consumption can temporarily alter the color.)

When you use the bathroom generate spittle in your mouth. Lean over the sink or toilet and let it slid out of your mouth. It should do so smoothly and with little to no residue left hanging.

If both of the above aren’t true then you’re dehydrated! Aim for drinking half your body weight in ounces in fluids a day. 150 lbs. = 9 cups (8 oz.) per day.

Do that and if you find that you still can’t sit through dinner without pain please do see your PCP.

I don't if the flight is long and it is bigger aircraft (two aisles: A350, 787, A380, 777, etc). I try to be up and moving around as much as possible. No booze. Eat light if at all. Drink water.

Do you have some kind of condition? Flying is uncomfortable but it's not typical to be in "excruciating pain"

EDS? That's why I hurt when I sit still too long, my joints literally slide out of place without muscle activation to hold them steady

Mid Forties... 20 hour flight. Agony. No sleeping, got up a bunch of times, didn't stop joint pain, back pain... Ugh. Some people can't sit still for that long without issues.

Off the top of my head: Stretch? Try to get on the plane later than most people? Take a sleeper train instead?

How is it while on the plane compared to after, are your knees hitting the seat in front? Maybe try a neck pillow to ease neck/head stress? Compression socks for foot, ankle or calf pain?

So two things to add to what others have said.

One, compression socks are a game changer especially for longer flights. Helps me a ton.

Second, this might sound weird, but do you have your tonsils and have you had a lot of cases of strep throat? Both me and my sister both have had our tonsils out as adults and it basically magically cleared up a bunch of joint pain I had.

I used to have excruciating knee pain if I sat still too long. Like I almost collapsed getting out of the car once cause I had dozed off for an hour or two and it made my knees hurt so bad.

Now I don't have nearly the issues. It's something to do with strep liking to basically hang out and cause inflammation in your joints.

I'm not gonna lie to anyone reading this though, getting your tonsils out is fucking miserable... When I went back in for my post op checkup the nurse said they had a patient earlier who had a purple heart and he had apparently said he would have preferred to be shot again over having his tonsils out.

Still worth it in my case anyway (not just the knees, had an infection and tonsils were giant, inflamed shit heads that kept causing issues)

They serve alcohol on planes.

Walk around the cabin every few hours if it’s a long haul flight. For a 5 hour flight, maybe get up once or twice. Get an aisle seat so you won’t disturb anyone when you get up. You’ll also have a litte extra knee space towards the aisle. Bring along ergonomic support like pillows for your neck or lumbar. If you’re really hurting bad, you might have an underlying problem that your doctor can help you diagnose.

Do you have scoliosis?

• (I will be so happy when transporters get invented)
• as others have mentioned, outside of an actual medical condition, best you can hope for is mitigation
• compression socks, neck pillow, eye mask, noise cancelling headphones
• stay hydrated – one of the big drivers behind jet lag is plain old dehydration
• aisle seat – you can get up, walk around a bit, hit up the bathroom, all without having to climb over your neighbors every single time

Arthritis.

I'm in my 40s, have slight arthritis and some other issues, and fly from Tokyo to the US sometimes. I generally don't have too much trouble, and certainly nothing described as excruciating. I do get up and stretch a couple times, usually when going to the toilet. You may want to talk to a doctor if you're in that much pain.