Since I had some injections into my knee the DR has made it worse for me everyday now that I cannot sit walk or sleep the pain is her renditions that my meditation is not working anymore and that is morphine tablets two four times a day.
Pain in knee: Since I had some injections into... - Pain Concern
Pain in knee
Sometimes it helps to have more than one pain med, for example for my recurring sciatica I'm currently using slow-release Tramadol, last time I used slow release Zomorph. The theory is that long term use of one thing your body gets used to it. And I always use the slow-release versions; tablets which release their medication over 8-12 hours.
Just to add to Dans reply.
Most medication starts wear off in 4-6 hours, so you will be in pain when you wake up and when your next dose is due. I have a knee issue and I take pain patches which last days rather than hours (still wears off near the end). I also take Amitriptyline & Gabapentin as there is nerve damage - so may be worth a shot.
Also, most GP's don't have in-depth knowledge of pain/ meds; so getting it referral to a pain specialist could help might be a good idea.
Is there any reason why you can't take NSAIDS?