Building muscle in the topline and around a weak stifle

My horse has been in training for the past four months and has improved drastically in the past few weeks with a more consistent schedule (yay spring!). She still has a “sewing needle” trot early on in a ride, but will stretch out, accept contact, and relax later. I am, however, always looking for ways to make things easier and more comfortable for her, and I don’t think she has all of the muscle that she should. I’m also trying to lose weight (tack and I are not 20% of her weight but I’d like to be 15% or under).

Her vet has told me that her SI damage is extremely minimal for an 8-year-old OTTB, and she does not have a “hunter’s bump” or any sensitivity to palpation in that area. She did have a spot of back pain that was injected and has not seemed to bother her since acquisition of a new saddle. My biggest concern is her right stifle. Her left is obviously stronger, and while she does move soundly in both directions, she is far less balanced when going to the right.

Vet, barn owner, and trainer all agree that this looks like a simple weakness and insufficient muscle around the joint, and it does not present like an injury. All three suggested hill and pole work to strengthen the muscles and stabilize the joint.

I am wondering if anyone has suggestions for how to do these things for maximum benefit to the horse. Lunge over poles? Ride? Hills how many times a week? How long should I do these exercises for?

Hill work and trot poles.

I prefer to RIDE, as I get the added benefit of working off more calories myself.

I have a hilly farm and like to get my mare out and do laps and serpentines of trot sets up and down the back field which has a nice slope (not too steep, but enough that you feel the horse’s balance changing on it).

I"ve thrown in the trot poles but quite honestly my mare gets so worked up when she sees the poles that she makes a bid and tries to canter them every time. Then I’m suddenly working on getting her to relax and not make a bid for them, and I feel like the whole purpose of the ride has then gone out the window.

I"ve seen an amazing change in this mare’s back since starting her back in work. The first time I noticed, I actually thought there was something wrong with her, I thought her neck was swollen, but turns out it was that spot just in front of her withers filling back out. Then her back muscle started filling in, first noticed in the rear, and then more in the front, near the withers now. Everything else is tightening up nicely too! What a difference regular work makes!