I have a ruptured ACL, torn LCL, cartilege etc etc you know the story. Full
surgical reconstruction. I wear a brace as pictured.
Brand is Donjoy - about $200
Check out www.kneeshop.com for some ideas. The support pictured is ideal
for kiting cos its made from wetsuit type material and doesn't rust. It has a
complex (double) hinge which mimics the hinge nature of a real knee. The
support prevents hyper-extension and dislocation due to rotation. It won't help
much with sore knees from chop impact however. The support won't make
your knee bulletproof - if your knee is completely blown plan to spend $500
on a more robust support.
Take the supplements mentioned by others, and most importantly keep the
quadruceps REAL strong. My physiotherapist used to strap a 25 kg weight
boot to my foot and get me to do straight leg raises - they really help to
stabilise the knee. Avoid kiting with your front leg held straight - instant
sore knee when you get off the water.