Thank you ALL for your kind words and thoughts. They must have worked.
We got excellent news--better than we could have expected!
She confirmed the diagnosis of a luxating patella, but only a grade 1. And she said that she sees no reason for us not to be able to do agility!
As for the limping, could have been the patellas manifesting in a weird way or could have been muscular. But she did point out a lot of musculoskeletal deficiencies that Lexi has and one of them caused her severe TMJ which has thrown off the muscles in her neck, back and pelvis trying to realign. So her neck and hips are all out of whack-- and she will need regular chiropractic alignments to re-teach her muscles along with some serious rehab exercises to strengthen the tendons in her knees.