This is more of a Kentucky headcanon 

Kentucky's war injury has become so aggravated that often, he has to wear a brace which was a fight in and about itself with his grandson 

It was harder to get him to realize some days he needs a cane tho 

Like he already has to hold onto someone (mainly Georgia) on bad days when he's walking, obviously all the farm work he used to do aggravated it, not to mention the car work he does now. It makes sense some days he needs the cane. 

Also Michigan and Kentucky are friends and sometimes go looking for old cars to fix up together.