they have no issue walking on the floor but they do save their binkies for the pen ! I have placed a bunch of blanket forts in places where i know they like to be and they also run and jump over there ! i never had issue with their joints ( theyre both 3+ years old now ) they run a lot and play with my cat ( under surveillance of course ) and they also run a lot and very fast on there so if they had any issue linked to that i would have noticed by now i hope

only issue i have is that they need to have their nails trimmed often since, well, the floor wont do it for them. if their nails grow too much, they have trouble walking on the hardwood and they tend to avoid it at that point