I agree Mike,
Your scan looks clean with no obvious cause for restricted flexion and extension.
When I have this history I think first of OA changes,
Then I consider pathology such as synovial osteochondromatosis or anything else that can generate loose bodies in the joint.
Joint pathology such as RA, joint effusion, synovitis gout etc are all on my horizon.
In your case I can’t see any of these things.
The plain radiographs have to be examined carefully.
So I agree, nothing on your scan to explain the symptoms.
Steve