Rheumatoid Arthritis Support Group
Rheumatoid arthritis is a chronic, inflammatory, multisystem, autoimmune disorder. It is a disabling and painful condition which can lead to substantial loss of mobility due to pain and joint destruction. The disease is also systemic in that it often also affects many extra-articular tissues throughout the body including the skin, blood vessels, heart, lungs, and...

But I'm about 95% sure it's not the MTX.
So I would see a PT and get some exercises. You may be pulling it getting the shot in? (Do you take shots or pills?) or perhaps you are more active after the shot? Do see a doctor or PT and try and figure this out. My mom had this in both buttocks, and she could barely sit. She did a million things for it, but nothing worked. That was over 10 years ago. Not to discourage you, but it discourages me. And she is better, since the early years, plus she has a hip replacement. Plus the PT said I might be genetically predisposed to this problem. Except she didn't get it for 15 years after I did, age wise. Not fair!
Not everything is a side effect of meds.
Assuming you haven't had any fat transfers or a butt lift [plastic surgery].
it has progressed over a decade and it is wicked tender. i sleep at night on my back with my feet drawn up like kids do - you know your knees are like a table?. i dislike this position intensely but side sleeping is gone with the wind. sitting is hard also like you are talking about.
i'm a mutt i figure. meaning i have RA and osteo and a lot of junk and disc compressions on pelvic mri's and on lower back MRI's and mid back MRI's. it's just part of the fun :)
for immediate:
have you ever had a pelvic MRI?
have you ever had PT for this pain?
is there a warm water (almost like hot water) arthritis pool anywhere in your commuting area? (sometimes hospitals have these and you can get your pt script directed there if you are interested)
have you ever had steroid injections into the bursas or the back? I have had these done by some quack (sorry he is not really but I get a kick out of this new specialty of pain management) called an "interventionaal radiologist/pain management - a lot of needle sticks. for me, they work for a while.
I considered facet nerve block things. and decided against.
My rheumatologist does not want to talk endlessly or really at all with me about my back and L5 S1 - she prefers I go over that crap with Mr. Doctor Needle Sticker or the Orthopedic or do physical therapy. She admits to being not in this treatment area. I find this problematic. I don't want more doctors.
in the meantime I love my ortho sit pillows - I think I previously put the link to amazon on here for them. I don't want to bore you.
hope this helps
feel better kiddo.
depot
Better just get up off my butt more!
Those facet injections can be a godsend. Spinal epidurals can also be a complete relief. I've had the latter. [I've got RA, PsA, AS, LGMD, OA, spinal stenosis, compressed discs galore......]
I did a full set of stretches and rode my inside bicycle last night. I only made 20 minutes on the bike, because the left buttock was hurting so much. Last time I pushed it, I made it so much worse.
This morning, I have hardly any tenderness! Coincidence? I might have to do this daily, if it works like this. Who knows, maybe it will even go away?? Just wishing out loud!
they don't make those british round ones anymore that I was scoffing at amazon
try this
https://www.amazon.com/dp/B01LYO93WD?psc=1
depot
depot
she describes the sit muscles and that is where mine are. As someone mentioned here, sometimes i certainly do have pain back there from either straining my hamstrings or plain old sitting too long, which shortens up the hamstrings.
doing the method I do, plus some mild yoga stretches ( i can't seem to do more than that) and my other favorite all over pain reliever (non medicine) is my dense foam roller. Wherein I roll on top of it, sort of like it is a rolling pin , and I am a pie crust.. ha ha.
I got that, also on Amazon.......many different sizes and lengths. They sell at Target, etc, also.