Abby,
I am so sorry to hear they are putting you through the ringer so to speak. It is bad enough you have to live with a swollen painful knee, and to be told to see the orginial OS first sounds so frustrating.
This posted after Jamie's post and I agree with what she said.
The challenge I had is all the surgeons I saw knew each other, or of each other even though they were 200+ miles apart.
Yes, you can have an MRI. I had an MRI at 6 weeks on my left foot, no problem.
Some things he may order are, blood tests for infection/inflammation, he may aspirate your knee for infection, he should check for ligament instability, bone scan for inflammation, CT scan, MRI, and of course an x ray.
If he only takes an x ray and says everything looks fine, stand your ground and ask for the above testing.
No matter what, you have the right to have a second opinion, what ever he says.
(((((HUGS)))))