grumplestiltskin said..Unfortunately, for me, its more than just softer riding boards, or flatter water (thanks Keef thats real helpful

).
My knees give my grief even if I walk too far or try jogging etc.
I know there is an underlying problem, I'm just trying to reduce the effects.
Wearing a standard elastic kneebrace afterwards helps, but if I can reduce it in the first place that has to be better.
I gave up jogging years ago because both my knees have had bits taken out and even power walking can aggravate them.
I use knee friendly boards and race sails with skinny mast. A softer sails really helps to smooth things out.
Every now and again I tweak my knees so I do have a brace, it's a heavy neoprene sleeve with stainless hinges that strap below and above the knee. Do a search on the web, you will find a variety of braces for water use.
To be honest I'm not sure how well they work but they do provide a level of confidence when I sail with an injury, but I am very careful.