My mare is being worked out of lameness right now...or trying at least. Right now, she is to be hand walked for 15 mins daily...after a few weeks, she can start interval training....walking for 5 mins, trotting for 2...after a few more weeks, she can be lightly ridden. Same thing, walking for 15...then a few weeks later, walk for 5 trot for 2 etc etc...vet said it would be a while before she could canter/lope under saddle. Mind you, my mare is very close to sound. She has not had any major surgeries or anything like your mare. But maybe this would help your girl too? Also, I'd try to stay out of the round pen if you can. The constant "turning" in a round pen really isn't too great for their joints. From what I understand. Also, TAKE YOUR TIME!!! TAKE YOUR TIME!!! I've seen TONS of ppl think their horses are all better so they speed up the recovery rate...and end up laming their horses all over again. No matter what, pick a slow speed and stick with it. Hope she gets better really soon!!!!