Could it be the ground, it's like concrete around here and my mare who has similar issues (vet very pessimistic about her long term soundness, wanted to operate six months ago) became very "off" a couple of weeks ago including tripping quite badly on one occasion.
I've come to the conclusion with my mare that her "flare ups" occur when the grass is flushing (as it has been over the last couple of weeks and six months ago), her coat is changing and as a coincidence, the ground is exceptionally hard here ergo unforgiving to her joints. Even though she is a hairy native, her stomach is very sensitive (she colic'd 10 months ago as well) and anything that unsettles it seems to cause an inflammatory response in her legs. We had a laminitis scare in the spring too. I completely reassessed her diet, found a vit/mineral supplement with pro/prebiotics etc in it, fed her salt, vit e, an organic herb mix, soaked hay, Naturebute (which is boswellia) muzzled her to try and get her weight down. I started quietly walking her out to get her moving after she'd had about six months off. I am a light weight rider and as my farrier and Physio said, providing she is happy to, there was no harm in riding her and was better for her - indeed she improves with warming up.
I am taking it really easy with her ATM as she wasn't sound last Friday so I upped her Naturebute to the loading dose, gave a couple of days off and rode her again on Monday and again today, quietly. She appears sound, doesn't object to the saddle or to me mounting and with all her issues, getting her moving more is better for her.
She had a period without hind shoes on for about 8weeks whilst she was really lame and I feel this helped as well.
She went from having hardly any changes in her hocks on New Years Eve to having a bone spur three months later. Prior to this bone spur she had had 3 hock injections and Tildren, none of which worked
so hence me trying the diet/life style route as I had nothing to lose.
It's really hard knowing what to do for the best, only you know your horse and your circumstances. I know I mentally gave myself six months to a year to try and get my horse sound (she's only 12) and I am paying full livery (with DH moaning in the background).
Best wishes.