What did the vet say ? If been good and now going, something somewhere is bothering her and it's not in her knees. It may be somewhere else and this her making the correction.
Shoeing wise, hope you have confidence in your blacksmith. The best shoe I used for a knee hitter was a queens plate. Broke over better and still had a little grab.
Just re-reading this thread. That's what I put on Cannae Barron, and I totally agree. Also, just because you're using the same blacksmith you still need to monitor the hooves yourself. Blacksmiths have a way of following the foot out instead of correcting the flares because they want that wall to nail into. Over time
, the foot gets out of shape causing soreness and gait changes. Think of a flare like having a too long fingernail that gets caught on something and pulled up away from the meat underneath. A flare is the wall getting pulled away from the laminae. Very painful.