it wouldn't hurt to just see your doc for an overall eval of your shoulder. it may or may not actually even be related to your previous injury. while you 'could' have some level of actual arthritis going on in there, that does not mean that other things can also happen in there too, ya know what i mean?
the one thing about shoulders is they suffer ALOT of wear and tear over time and can show it in many ways. there is whats called the rotator cuff which makes up the entire shoulder area including the major joint itself along with tendon and ligaments that just give that shoulder the very wide range of motion it has. if any particular terndon gets torn(happens very commonly trust me) it will show itself with either loss of ROM or alot of pain/burning type of ick for us to deal with.
i was having burning in the shoulder and the top muscle there in mine for many years. i di do something to it many years ago while lifting wieghts one day. well it came back to haunt me on nov 6 07 when i went to lift my purse up off the top of my fridge like i do every single morning and i felt this pull in the area from the base of my neck and on over to the top of my arm? i immediately had to drop the purse since i just totally lost the ability to continue to pull up? found out after MRI that i had a TON of wear and tear damage along with a completely snapped top tendon(the one that actually runs from the base of the neck to the top of that shoulder area) along with another right under it that was just partially torn too. did not have a clue things were just that bad in there til the MRI was done. but when my primary even tried to just do that eval on me the day i saw him and run my arm/shoulder thru all the many different ROMS? no go with some of them, it just would not either move that way anymore or the pain made him have to stop.
i seriously would just see your primary for that eval and see about at least obtaining that needed MRI on the shoulder itself. plain old x ray would only show the joint and other bone there and NOT the very important tendons and ligaments that you just really to need to see right now considering your symptoms. i was told by my ortho that rotator injuries are one of the most common they see in their practice, next to knee injuries that run a close second. there is just alot of different structures up in that shoulder/rotator cuff that get damaged over the years or with a sudden pull type injury too. it just needs a thorough eval just so you know what it is you are actually dealing with. never ever just assume anything when it comes to our bodies. you just do not always know til a scan gets done as to what IS an underlying reason for problems. that much i found out many times the hard way. please let me know what you find out. good luck, FB