Best bet to avoid injury (without braces) is to build strong muscle tissue to protect the joint. Concentrate on leg workouts in the gym, and practice balancing on one leg. I know it sounds dumb, but it does work and was a recommended exercise, by my physiotherapist, after a nasty knee injury. Once "plain" balancing is too easy, work on juggling a ball or similar at the same time. This works to throw you off balance and force the knee to work. Maintain a slightly bent knee while doing these exercise. If your really keen, you can build yourself a "wobble board" (a 16' square board with rockers installed on the bottom), and do the same exercises.