Our mare has always drug her hind feet when she is in her stall or walking around leisurely. Lately I've been noticing that she looks extra stiff in her hind and every now and then she will be lame for a few steps
I presume you mean she has always dragged her feet, not that she is drugged??
I don't know much about the condition, but recently acquired a pony with 'locking stifle' who does this occasionally, on one hind leg. He is not lame, or apparently uncomfortable because of it though. If he were, I wouldn't consider riding him until I'd got it sorted. It is apparently a conformation thing, that he was most likely born with.
The vet & bodyworker I consulted about this prob said he was a bit tight in his hips tho, probably due to moving differently to compensate for the prob. They said to keep a close eye on it & he may need a bit of work every month or few to keep this from becoming worse. Touch wood, he hasn't had a prob, but I get the bodyworker every so often anyway, for a Bowen treatment & checkup.
Your first para talks about 'mucking' & doing not much else over winter. Does this mean the horse was kept locked up? Horses need free movement, or at least a LOT of in hand exercise, **regardless of weather** if caged, and even if turned out in a paddock, may be rather sedentary. Lack of exercise could well be the cause of the condition worsening. If it is a patella prob, this is also more of a prob if the horse is allowed to become unfit.
MIL also said that the only way to determine what it is is to put Lily out and have them do MRI's and x-rays to the tune of $3,000-4,000 which I cannot do right now. She suggested riding her until she goes dead lame. I am not comfortable doing this.
How about you get her
to piggyback you until she's 'dead lame' & see how she likes it??? She is right that you *may* need MRI or such to determine or confirm the prob, but a *good* equine vet or bodyworker should have a fair idea of what it could be & how to help it. A bodyworker(chiro, physio or such) will hopefully be able to straighten her out so she's not hurting in the meantime too, assuming it's a hip/back/patella prob. I would not ride this horse at all, but turn her out 24/7 if at all possible & continue low-impact in-hand exercise if she can do it without pain. When a horse *shows* lameness, it is likely that the problem is fairly chronic. Horses being prey animals are great at hiding their physical probs until they're too bad to ignore.
I appreciate that MRIs & the likes are expensive & so therefore difficult for many to afford. As suggested tho, you may well be able to do without that expense. But owning an animal means you have taken responsibility for it's wellbeing, and one condition of this means treating the animal *appropriately* when the horse is sick or suffering. It is classed as neglect & cruelty not to do this, regardless of the state of your finances. Not trying to have a go at you so much, as you sound caring, but sounds like your MIL possibly isn't very caring & has been in your ear with some rather irresponsible advice.
I'm not sure if I should call my regular vet who knows Lily or a chiropractic vet. There is one in our area and I have heard good things about him but he is expensive. Any opinions?
I would personally go the chiropractic, as if your regular vet isn't experienced in this type of treatment, he could be a bit cheaper, but useless.