As you probably know from Jane I have had bad knees for many years and at times been unable to walk so I can empathise with you Steve.  I found the frozen peas extremely helpful and a pillow under the knee at night also helped to relieve the pain.  Thankfully with regular exercise my knees are now holding up well but on the occasions when I twist them and they swell and become very painful I use Inacid 100mg (indometacin).  It is a prescribed inflammatory/painkiller and for me it is in suppository form  (very much the norm if you live in Italy) but according to my doctor comes in a gel form also. It is the only medication that worked for me and works for several hours.  Just thought it was worth mentioning in case nothing else works for you.