Their coats get so matted that they have to be shaved off in one giant pelt.
Their toenails get so long it changes the angle of the bones. This not only causes joint stress leading to pain and arthritis, but also increases the probability of a broken leg.
Mats end up in places you would not expect. In the below picture, the dog has a giant mat growing from deep inside the ear. These mats are also often found between the pads on the bottom of the dogs paw-a place most owners do not usually check.
These mats, the size of my hand, were cut from the bottom of a Cocker Spaniel's ears. On the right hand mat, it is easy to see where the rounded bottom of the ear flap would fit into the curved cradle of hair from which it was eventually freed.
