Not my horse, but a friend's. Mild, but chronic, not terribly lame but had started landing hind feed medially in walk and trot. Ultrasound showed lesions in both hinds: PSD.
Horse had shockwave (four lots a week apart I think), cartrophen injections and careful rehab (lots of walking on hard, even ground), and has come back 100%, competing Advanced Medium.
Ditto Halfstep with another horse- exactly the same prognosis ( tho not quite as bad ) and same treatment. Horse now making super progress. Its a funny condition, cos once treated, it really improves with the correct work. Teeny improvement seen 2 months after treatment in which horse had light work. In the 3rd month the work stepped up a gear and a big improvement was seen. Complete rest does not help things.
There are a few advanced eventers, one who was on the GB team that have had the operation for more serious PSD and returned to eventing at International level.
My boy had it as a 6yo in just one hock.
Treated with shockwave and a controlled return to work.
Played around for the next 5 years at OPN/BD Nov/BN/Discovery, that hock never really caused an issue although he had spell off with other injuries. Then decided he wasn't going to jump again and concentrated on dressage. Did 6 months training at a good medium level and played with canter pirouette etc and competed at a few elementaries before the other hock went
Plus I know one horse that had the operation in both hinds, done by Sue Dyson I think. This one came back to full work as well so far as I know. But I think the operation is usually more sucessful on acute rather than chronic PSD (can't swear to this).
Had operation on fairly mild PSD on right hind; box rested two weeks, small paddock rest for two weeks then turned out for 6 months ( my choice as he doesn't do walking in hand!!) started ridden work, walk only for 6 weeks then introduced trot, building up to 2 hour hacks 5 times a week over 3 months.
Started schooling after that and he has been back in full work, fun rides etc some small jumps and schooling for 8 months without any problems.
Infact he is going better than ever!
Jesper was diagnosed with chronic PSD when he was 5yrs old. Treated with shockwave and rest. Returned to work sound. We made the decision to not jump him as he showed more promise as a dressage ride anyway. He never used his right hind quite as well - scans showed it was healed, he was definitely sound but he always favoured it slightly.
Aged 10yrs he was diagnosed with collateral damage in his left fore. He briefly returned to work as a light hack but despite extensive treatment for this he is now lame behind. Vet and physio agree the extra stress has caused his hind suspensories to go again along with his sacroilliac so he is now retired.
So basically, mine would have been a positive story if it weren't for other injuries. The prognosis is normally good but it can lead to compensatory injuries especially in the scaroilliac area. But definitely not all doom and gloom.