(chuckling) Recenly, I have had to learn a whole lot more about how knees are built and work. I can now spell 'meniscus', though I have no idea what the plural is. I could happily have done without this increased knowledge, but years, okay, decades of use, misuse and work have me in a place where both are simultaneously failing in the same way, though mercifully they alternate rather than both at once. So far.
Braces, though, interesting.. There's the ones with hinges and those without, a lot of velcro and those that slip on, seems like anybody who can make one has.The field is definitely open.
So - one for surfing and ( open up the market ) most water-related pursuits. Needs to be water and corrosion resistant, needs to work either on top of a wetsuit or without a wetsuit/under waders let's say. Nothing hard and projecting ( wetsuits, waders for fishermen, and surfboards would suffer), fairly compact so it would work under some things , deal with water and air temperatures from, say, `-10°C to 45°C (salt water winter diving or snowboarding to surfing the tropics ) reasonable impact resistance/protection ( I bump something with the knee, now, and the screams bother the wildlife) .
I'd suggest something with hinges, replaceable nylon or HDPE T-washers/bushings to handle wear and friction, probably of either relatively light construction stainless or thicker and really really well coated aluminum. CAD/CAM. I've seen polycarbonate components for similar stuff, but between bulk and my possibly unreasonable fears of a brittleness/glass transition temperature/UV degradation thing going on I'd stick with metal.
Positive buoyancy? Yeah, okay, but just barely so in fresh water so it wouldn't immediately sink to the bottom of a pool or stream or lagoon if it got dropped. .
Washable in fresh water and soap, so you can get the salt out and not get salt water chafe sores.
As this little thought experiment proceeds, a couple of things are coming out of it.
First, it'd be really complex to make one something that'd do everything, a 'swiss army brace'. Or a bunch of variations that would be expensive, complicate the development and make keeping all the models in stock a lot of no fun. Might want to make it modular, ideally with various components that snap or velcro on or off, for different sizes and uses, I think the components would be easier to develop, manufacture and for your customers to keep in stock.
.Next- yeah, a surfing brace is nice, an all-watersports brace is better and opens up your market a lot. And anything that would work for that is actually a really good general purpose knee brace that, as it happens, you could use surfing or general active sports too. Which might be a good way to go, nobody wants to have to lug around a bag of various braces for surfing, hiking, bike riding, formal wear, what have you. Again, a modular approach might be your friend. Plus it's a lot easier to make and sell the incremental improvements as components rather than the whole thing, cost issues if nothing more.
And there's also the King Gillette model to think about. Yeah, King was actually his first name. He gave away the original double edge razors and got quite rich selling the replacable blades. Selling the components (which unlike the basic knee brace could be patentable) might be your profits.
Keep us posted. And if you need a beta-tester...
doc... just call me Gimpy