In reply to Rog Wilko:
It makes no difference to you that it will take three weeks to get the result.
It's not broken, so the answer is rehab/physio.
As it's not broken and no trauma, the xray will not show anything that cannot be improved by rehab/physio/exercises.
If it is your first knee problem there is nothing to be gained from catastrophising about replacement; see a physio for rehab exercises.
No idea of your finances, but it would be a wise investment to pay to see a good knee physio who can diagnose it and tell you what you need to do to rehab it.
You don't need to see physio more than once if you can't afford to; just become a machine about the exercises.
I think it is a bit shoddy of the physio to delay getting on with it by waiting for a xray which won't show a break and won't show anything that delays rehab/exercises.
If the physio won't see you until the process is followed of waiting for a result which won't show a reason not to start rehab, go find a physio who can think not in terms of process but in terms of clinical assessment and rehab.
DOI I am not a physio but I deal with knee injuries pretty much every day at work.