Final Video:  A 9-year-old Miniature Schnauzer has trembling hind legs - IVDD or slipped disc
Channel: Dr David Sing
Date: 2017-07-10

Hind limb weakness and trembling. X rays show reduced intervertebral disc space. The discs shrink due to old age. 
The spinal nerves are compressed, leading to pain in the hind legs. Hence there is hind limb trembling. 

The dog continued to have hind leg trembling but was otherwise able to walk, pee and poop.