Thorns in paws

Fred put about 20 miles on this weekend, and on the way back to the truck he was noticeably limping… so I checked for another thorn and nothing, still a lump, but nothing. When we got home it was noticeably swollen, and he didn’t want me touching the paw at all. Of course, I made him let me check it out, and still no thorn, no puss, no noticeable “hurting” spot other than the swelling.

Could there be another small piece of thorn still in there that the body didn’t push out? Or could it be just like a bum knee coming back when it’s cold or over used? Do you think some paw cover of some sort would prevent the swelling after miles on track? I don’t know, and just figured I’d asked. He is putting some more pressure on it today…

Thanks.