Thanks for placing your query here.
I can appreciate your concerns.
It seems that the primary problem is in rightt knee (swelling, pain, inability to flex) & the muscles below knee have become thin & weak because of relative lack of use (so called dysuse atrophy
you should consult with an orthopedic doctor to find out what is wrong with knee .
are the minimum tests required.
Hope I have answered your query.
If you have any further questions I will be happy to help.