I've just had a GP appointment and she's going to chat to the Pain team and a pharmacist about what's possible.
I can't take NSAIDS due to stomach surgery, steroid injections have stopped working (in knees). I already take gabapentin for sciatica but it does nothing for knees.
What's left? 
I asked about Diclefonac and she said it was just high dose ibuprofen and not used anymore.
I have arthritis in both knees, one hip, and one foot. I'm massively struggling to walk up stairs - crawling quite a bit - loads of pain now. No problems walking on the flat or going DOWN stairs.