Some places have indoor pools for dogs to practice dock diving, etc. You could check around to see if there's one nearby
Just thinking of a low impact exercise that won't be hard on his hips.
Jasmine - Female Miniature Poodle - born Aug 15, 2010
Loker Delgado Von Stalworth - Male GSD - born Jan 26, 2012
Koda & Zazu - 5 year old male cats
Alex - Male Cocker Spaniel (rescue) - RIP Cuddlebug 2007-2010