First of all, again, this is not my mare and so yelling at me to have the miserable thing
euthanized to make room for all of the young horses in the world isn't going to help. Not my mare, not my facility, not my call. What I may or may not put to sleep is not what the owner of this horse rescue/sanctuary may do. I have a habit of rescuing trainable horse and training them. She has a handful who will remain on her farm forever, she enjoys them and if they have a home who are we to judge.
Second, this is a 6 year old horse, "age" doesn't matter in terms of health.
The mare is not in a great deal of pain, PunksTank is spot on. I am sure she isn't completely comfortable but neither am I! Arabella is very happy, she is extremely sweet and if this is the face of a horse who needs to be immediately euthanized then ...
As you can see in the video, baking isn't her strong point. But she walks around just fine. Lies down, gets up. She can trot and canter, play, boss pasture mates around and function completely normal. When I first saw photos of her I thought stifle but that is clearly not the case when I went to visit her. Nothing locks, pops, slips, snaps or is otherwise obvious aside from the fact that she walks a little funny, mostly, just stands funny. Running a hand down her spine gave me no indication of pain, hitching her legs up and trotting her off did not change or worsen the issue. To my knowledge a vet looked at her enough to conclude that she is not in major pain (which any knowledgeable horse person can see when they mess with her in person) but they have not done anything to "throw money at" what this actually is, or why.
That was where the asking for ideas came in. I suggested she get her on a magnesium supplement and have a chiropractor look at the mare but I really do not think that this is something that will "fix" with an adjustment and a can-do attitude.