Jazz knees

Having only recently learned about the Jazz funeral and seen what it involves I can’t help wondering about the knees on the man (or woman?) who leads the procession. Also, in the various parades where they do the dipping dance. I have this resounding wonder about their knees and how they manage to support their body weight doing all those moves and not get trouble with their ligaments? The parades must go on for miles and yet they never loose the moves. Or perhaps the one I saw was a more adventurous dancer. In anycase it’s a great send off they give you.