Hi, my first question is do you have her on any type of joint supplement. I suggest one with glucosamine msm and HA. Next, I would suggest starting her on a joint supplement if not on one already and also start her on a product called STP or Stop the Pain. Its an all natural pain reliever no bute in it. I have several of my top performance horses on it. Including my 11 year old harness racing stallion l, it makes him feel great and has never upset his stomach ever. He races and still acts like a 4 year old. He is a picky eater and never refuses to eat grain with stp in it. If you do not see any improvement with these options i would definitly suggest having your vet back out to re-examine her hocks and do flex tests etc. she is an older mare doing a tough job so definitely get her started on a joint supplement and stp as soon as possible. Also after you work her if she has to be stalled make sure to rub her legs down including her stifles with a good liniment product. Oh and lots of cookies!! Good luck and have fun riding!