It could be DM and it could be a back injury or a stroke in the spinal area (google FCE).
A sudden onset seems to be more like an injury.
But since he had something slight before hand maybe it was the onset of DM.
It is hard to think he would have had a working career if he had hip dysplasia....I am pretty sure departments normally x-ray dogs before starting their training.
NAPWDA Certified Cadaver Dog
Waiting at the Bridge (italics
=GSDs) (hemangiosarcoma=blue):Grim , Cyra, Toby
, Rainbow, Linus, Oscar
, Arlo & Waggles