First of all, I am so sorry you are going through this! I certainly can empathize with you and know how heartbreaking your situation can be. I also recommend trying an equine lameness specialist to really narrow down the diagnosis and a good chiropractor may be something to try as well. I’d prefer a vet with chiropractic experience for a horse with lameness issues…just for ease of mind.
My riding horse, who is also my first horse, has also been retired at a young age (14). I have a younger horse, but he is not old enough to start under saddle yet and I honestly still feel I will never have the same bond with another horse. It can be really tough sometimes. My 14 year old was having on/off lameness issues for about 2 years and no local vet could give me a straightforward diagnosis. It was always hooves, abcess, maybe the hocks (although they flexed fine), or we don’t know. So, I finally decided to pay for a lameness specialist to come down and although the news was not great, I am so glad I finally had a true diagnosis that I could work with and make peace with. It was 100% worth having a specialist down and I would have saved a lot more time and money if I had done so in the first place. My horse was diagnosed with something called DSLD (degenerative suspensory ligament desmitis or ESPA). It can be very hard to diagnose within the earlier stages and is a whole body disorder, but the telltale sign is usually hind suspensory ligament damage which eventually covers the entire ligament. It is something I would potentially look into with your horse or just ligament issues, since hind end issues often occur with hind ligament issues. My horse started to present a funky canter early on and would go in/out of it consistently. It can begin to look like hock issues early on and hock injections may make it subside temporarily because the injection can ‘leak’ down to the suspensory ligament. From what I’ve heard from others, It can present itself differently in every horse. The specialist diagnosed it via ultrasounds on both hinds.
I do know someone else who was working with the same specialist trying to narrow down the issues in her own riding horse…Issues that have been present for years: lots of arthritis. She had tried everything including injections, shockwave, PRP and I’m sure some other things too. The lameness would subside for a few months and then come back everytime. She sunk a lot of money trying to get this horse sound… over $10,000. That was 2 years ago and the horse still isn’t sound, but happy to do lower level work. I think sometimes if we have the best vet on the job and still can’t fix the issue then we need to face the reality and accommodate.
At one point, I was considering vet school and shadowed with several vets, including small animal clinics. A few vets on staff had solely started out with horses/agriculture and then decided to go the small animal route due to a few reasons- often money and safety, but other reasons as well. One vet in particular was quite open to me as to why she decided to move away from horses. She told me blatantly that she didn’t agree with the common route of treatment for lameness in horses, particularly injections. Now, here is the thing; Injections are temporary and often are a ‘masking’ treatment. They are a very useful ‘tool’ no doubt, but that particular vet had seen so many people use them and then continue to work the horse as if the horse had no issues at all. In reality, the issues are still there and she just didn’t agree with that philosophy. Now, I personally don’t think injections are a bad thing to help keep a horse comfortable, but I can see her point of view as a vet. So many seem to associate injections as a ‘treatment’, in the way they ride the horse, and not necessarily as just maintenance. Most horses like the work and it can be good for them, but once the horse has a chronic issue such as arthritis, it is there to stay. That to me, means I may keep riding, but for maintenance and not competitively anymore, as that could exacerbate the issue further.