Knee bracing for hiking?

[cmac]

I do a lot of hiking, going uphill is no problem but getting back down I get a really bad pain on the outside of the knee(s) to the point I have to try and keep the leg straight as I come down (not that easy). I have this problem on stairs and ladders to. The knee doesn't swell and gets better after heat and icing a few days. I use trekking poles to lean on. Maybe the uneven ground is stressing the on going injury. Would a brace help and what kind have you used that worked. Thanks