if you want it, HighlandHaggis?
I was struck down with a rare and life-long disabling physical illness when I was 21 so I understand where you're coming from.
Do you trust your medical team to help and support you? What sort of treatment have they offered you and do you find it's helping or not really? Might be worth having a word in the shell-like of your GP to see if there's anything they can do/give you to help with the pain in your knee and I recommend asking about if a TENS machine would help you. You can get a cheap and cheerful one for about £20 on Amazon - don't expect miracles from that one, but if you find that it helps your pain even slightly then it might be worth investing in a £70-£90 one to help you more.
The thing that you need to understand (and sounds weird until you try it) is that the electrodes go
at the sides of the pain not on it - weird, right? Thing is, the pain-killing magic goes between the two electrodes and if you put the electrodes on the pain then it goes through the roof and makes it worse for you.
I used to double the dose of paracetamol every month because of period pain and it barely touched the pain, but within a couple of minutes of using my very first TENS machine with the electrodes placed properly, I was totally pain free and it was a huuuge relief.
You don't have to live in pain and you don't necessarily have to pop pills either. Get your docs advice first though 'cos they are medical bods and I'm not