Have a mare that was off earlier this year so got a lameness exam done and ended up getting her stifles injected. She was showing symptoms of ulcers so treated her with omeprazole. Couple months later on the pattern, she was still stiff on the backside, very upright with her head, but using her hindquarters. She would just power down and get stuck. When loping she is stiffer on the left and has more bend on the right. Got chiro done couples times, massage, didn't see a huge difference. Noticed she liked to rest her back left often and sometimes point her front right toe a little. Got a suggestion from an osteopath that her pelvis had an anterior tilt. With their help, i believe i was able to release it (im not an expert). Took a video of her a couple days later, any suggestions?

Did you x-ray the hocks? (or stifles? Although bony changes there aren't common)

When you stretch her hind legs does she resist when you stretch them back ? Horses with SI soreness will resist their hind legs being stretched back and resist the shoer when shoeing.