Cat is limping but no sign of pain

I have a 6-year old male orange tabby.  A few days ago, I noticed that he is limping with his right hind leg.  When I pick him up and move his leg around, squeeze his paw or press on any part of his let, he shows no sign of pain or distress.  He actually purrs!  Should I be concerned? 

If he continues to limp, I'd be concerned. Cats sometimes purr while in pain, but if he's not objecting to you manipulating his foot and leg that's likely not it. Did he do something to a claw, or get something stuck between his toes? Does he go outside? Road salt can make animals limp.

He is an escape artist so he might have snuck outside when I was not at home (and my daughter was cat-sitting).  I'll check his foot right away!  Thank you.

 [endif]Limping is a sign of him being discomforted, and maybe only painful while walking.. Arthritis is most likely the problem here.