I too have a permanently mildly lame boy(as well as my accident prone mare). I do wonder, with only some basic multiple choice questions, such as this, what accurate info will come out of it for you. So here's 2 of my horse's specifics that I couldn't tell you just in the survey...
So... I chose 'more than 3 times' for no.1 but what would have been more appropriate was 'lame after hard work(too much trotting & cantering on the trail) so we avoid hard work & rarely notice a prob - pretty sure it's mild 'navicular' due to weak caudal hoof. Had a vet but no rads in the early days, has regular(about yearly if there's not burning need) chiro visits, which have ruled out other body probs, aside from being a bit stiff in hips & in the elbows - mild osteo arthritis now, as he's an 'older gent' & I now will get off him to go up or down steep hills because of this, which seems to manage it well.
My silly mare... she has had a couple of rope burns in the last couple of years, same hind fetlock. Each of those she was barely lame at all, but gave her a couple of weeks rest anyway. First of those I had the vet, a number of times, because swelling went to her hock & never went away(1st time nearly 2 years ago, leg still fat) except after exercise. Vets had no advice, short of bute & antibiotics(thought infection) short term initially. Wrapping it - as suggested by some here - did also help, but only lasted for a short time after taking bandage off, and I tried this for a few weeks before packing it in.
Then about a month ago, same leg... big fat lump on outside of hock! No apparent lameness or any tenderness with pushing or prodding & it was hard as a rock. Got vet who said likely burstitis, should go down, nothing much to be done aside from rest, but wrapping could help. Gave her a couple weeks of wrapping, but no apparent change. Cept she grazed it the other day. Now maybe she's got a permanent fat hock as well as fat cannon/fetlock! But nothing seems to bother her!