Following knee damage sustained during a very long alpine descent, I bought a pair of neoprene knee braces. I used them during my recovery and they certainly helped on downhills. I reinjured one knee again at the start of this year, just going upstairs, and for a while I had to resort to the brace again and after each walk I strapped a frozen gel pack to the knee. Although I no longer use the braces routinely, I still carry them and if a knee starts to twinge, I strap a brace on. I still use the gel pack too if I end up with a sore knee after a walk. The braces hold everything in place and keep the swelling down and the gel pack stops the swelling after I stop walking.
They may not suit your problem but they certainly worked for me.