Interesting topic, really good post by
@carthorse . Would agree with the majority of that.
I think the key to keeping to keeping them sound is keeping them fit for the work they're doing, a healthy weight, shod when they need it and varied work. Also think a lot is down to luck sometimes it's just the way the way the cookie crumbles.
I don't think working on a surface the majority of the time is great for long term soundness but then you could argue neither is concussion from tarmac. I know 2 horses who've done suspensory's neither hacked (nappy) and did a lot of amateur dressage schooling think circles. These horses are now coming back into work with hacking on roads, straight lines only, vet has advised lunging will be a no no in future and schooling will need to be varied. I think that in itself says a lot.
Thinking about the horses on my yard, majority can't walk in a straight line yet go round and round in circles. Circles seem a huge part of most leisure/amateur horses I know. From in the school to lunging to the horse walker, personally I don't think this can be doing the horses any good. Another thing I've noticed is horses left for months not being ridden then suddenly being ridden again and back in lessons the same week, planning fun rides the week after, with feet left up to 12 weeks before the next shoeing. To me that's a recipe for lameness but seems like people don't want to do the old fashioned fitness building of bringing a horse back into work.
Lottie is schooled to hack and hunt and does both very well, can she go on the bit? No, but I'd put money on her being the straightest soundest horse on the yard. She does work from behind and she's level you only have to see her trot to know that. She has hunted from 4 and that's all she's done since. She might be a creaky old lady by the time she's in her teens but she's had a lot of fun to get there. I do my best by her, she's kept very fit for the work she does and no way would I hunt/team chase her if I thought she wasn't at top fitness. I also do a lot of walk and trot work hacking to help keep the ligaments/tendons strong, shod religiously every 6 weeks, ice boots etc. I think if you over think it too much we'd never do anything with our horses or try and put them on wheels.