I feel your pain; My gelding has negative plantar and planar angles caused by a barefoot trimmer who knew a whole lot less than what he thought (prior to his arrival with me). It's pricey and worse, may be permanent because pasturing him (which would help a LOT) is out due to EPSM (genetic starch intolerance, essentially).
One thing that really helped Rebel (and as a TB, stall rest is not a whole lot of fun-he gets really owly) is backing up hills. Excellent exercise for the HQ, good for the stifles, and makes him think about his feet. Inhand work over cavaletti (eg poles on the ground) is good too, depending on what you're fighting. There are several good books on inhand work available on Amazon; Might help keep both of you sane.
Chief cook & bottle washer for one kid, a dog, 6 hens, 2 surprise! roosters, two horses, and a random 'herd' of quail.
~The ultimate ignorance is the rejection of something one knows nothing about and refuses to investigate~