Awesome race yesterday, aaand I found out what's causing my knee issues. Apparently I'm an over-pronator. So I got new Brooks to fix it!
New shoes do not fix over-pronation. They make you weaker by allowing it. Form corrections fix the prob that is due to heel strike
How do I fix it? Just start focusing on perfecting my footing?
You could start looking at your technique issues. Most people have technique tweaks that manifest themselves in injuries. It is those soft and supportive shoes that have been allowing people to run long distances with sloppy technique that leads to eventual downfall. People who have been running for a long time are more vulnerable than new runners because the weaknesses sneak up on you, especially as you age with such great aerobic fitness.
We have been told for so long that heel striking is the right way to run long distance, but that is so wrong. We were naturally selected to run with midfoot strike. The heel can be touching, but it should not be bearing the impact. Impact is dissipated by your entire body and not just your foot/shoe. Some studies actually show that the softer the shoe, the greater the impact, because your body needs to feel and respond to your foot plant! You mentioned you problem as being caused by pronation - the great enemy of all runners, according to the shoe companies - we gotta control that pronation! Well, if you run with proper technique, there is in fact little or NO pronation. All injury problems than go "poof" and they are gone (in time).
Tweaking technique is a real process of reeducation, unlearning some false beliefs put forth by shoe company marketing, and physical practice. And since most of us have been running in over-built shoes for so long, the process needs to be slow, or else there are a host of other problems that you could create for yourself by trying to change something too quickly, even though it is the right thing to do! The absolute best place to start is reading the book Chi Running by Danny Dreyer....