As said above.. keep your leg strong... cross training and strenght exercises... as we get older... everything needs more work to keep the same.
I ride with custom braces on both knees... CTi Vapor sports. it is so compact that I can wear it under blue jeans if I remove the patella cup.
I switched out from the DonJoy a while back... The DonJoy brace migrated (slipped down) too much for my taste (same PA fitting both). Also the CTi braces can be put on or removed with boots on... you dont need to "step through" the brace. This is personal preference and I think that the DonJoy is a top performer as well.
I'm a believer in bracing... Even for those with healthy knees... most Pro Moto guys wear bracing that have healthy knees
All of the brands offer OTS (off the shelf) bracing that fits most people but if your knees or leg is outside of the norm... best to invest in a custom brace.
Get a prescription from your doctor for a knee brace... most insurance pays for them.
I'm not a fan of the Asterisk as you have to lace it up to put it on.
Another OTS brace that is getting some attention is the POD-MX bracing.
I think Monte on the forums here carrys the different brands at Bobs cycle...Drop him a PM.
People seem to be very attached to what brand works for them...The CTi and DonJoy seem to be the "top dogs" in the business. A lot of pro Rodeo guys wear the DonJoy... the company participates in a lot of the events and puts out a lot of sponsorship that builds a strong following.
The fit is very important as well as something with Patella protection.
My 2 cents.