Or bladder issues…
A few years ago when my early retiree was a brand spanking new retiree I noticed him parked out all the time. Nothing else seemed wrong except he frequently looked like he was about to pee.
I also saw him frequently since we had a drought and I kept them in the dry lot 24/7 for about 8 weeks to give spring grass a fighting chance (it’s a really big dry lot). But other than the parking out he seemed fine. He also peed normally which I also saw often since his thing is to pee as soon as I come down to the barn to feed.
When I had the vet out for spring stuff and she thought it seemed like a bladder issue (up to that point I hadn’t thought about that, just that his way of standing reminded me of a horse about to pee). We tested his urine, it was normal so I scheduled him for a bladder ultrasound. Normal too.
The surgeon who did the ultrasound (and was there one who did most of our last ditch, kitchen sink treatment plan before early retirement) then decided to palpate his back, whereupon the early retire almost hit the floor he was so painful. Granted, checking his back would have been option#1 pre retirement, but the dude had been living his best life, untouched by anything human made other than an occasional halter and in his brief working days, parking out was never a symptom (making me a high speed land dart ranked much higher). So I took him home, gave him some bute and in a few days it was time to start adding pasture time to his day and the problem disappeared with movement (that didn’t involve a human on his back).
tl;Dr could be a bladder issue, but save some $, check the back first.