Personally if I was at all concerned I'd get the vet out PDQ to just have a look.
If this is happening on a regular basis (you don't say what the age/work of your horse is, or type) then I'd be having a word with your farrier and/or asking the vet for further investigations.
Some of the people I see hacking past my place put their horses in knee-boots. They're fiddly faffy things IME and the horse needs to get used to them, but if you are doing a lot of roadwork it does make sense.
I'd get the vet out tho' with yours in the first instance, just to make sure and ease your mind.