I have an old dog.  Sam is 14.  He has developed arthritis in his back legs.  He rarely lifts his leg to pee anymore.  Instead he squats more like a female dog.  I think the older a male dog gets, the harder it is for them to lift their leg and pee.  I can tell if Sam is having a good day by how high he tries to lift his leg when he pees!  I think keeping an eye on that as male dogs get older is probably a good indication of arthritis.