Just like any other living things, dogs will show physical changes as they grow old.
The most common physical manifestations of aging dogs are the following:

• Changes in weight

Because aging dogs are less active, the metabolic rates of their bodies change.
They will need lesser calories due to the decrease in energy requirement.
If you feed senior dogs the same amount of food you give them during their active days, they are bound to gain weight and might result in obesity problems.

• Changes with the hair coat and skin

You may start noticing gray hair around the eyes and the muzzle with older dogs.
What used to be a shiny and healthy hair coat may appear duller and thinner.
The skin of older dogs may also be prone to injury because it will become thinner.

• Arthritis and lessened mobility

Older dogs may suffer arthritis and would have a hard time moving around the house, jumping into the car and going up or down stairs.

• Dental diseases

Dental problems are common among older dogs.
But this can be prevented or minimized with a dental care routine like tooth brushing and regular dental check-ups starting when your dog is still young.

• Changes in behavior and activity level

Cognitive dysfunctions in aging dogs may result to decreased attentiveness, decreased activity level, restlessness at night, disorientation, confusion, loss of housetraining abilities and not being able to recognize family members.

• Impaired Hearing

Some pet owners may wonder why their dogs no longer obey commands.
It could be that the dog already has a problem with hearing.
Hearing loss in dogs is generally irreversible.
So you can find other ways to communicate with an old pet.

• Vision problems

You may notice a cloudy appearance of your dog's eyes and it is a condition known as nuclear sclerosis.
The dog may still see quite well but not as clearly as before.
Other conditions common among old dogs are cataracts and glaucoma.

• Calluses

Calluses will most likely develop on dog's elbows because they tend to lay down most of the time.

• Thickened foot pads and brittle nails

Older dogs will have thickened foot pads and brittle nails.
Because of inactivity, nails have lesser chances to wear out compared to a dog that is always running on rough surfaces.
So, you have to clip the nails of your old friend more frequently.
These pets have always been there for us during their healthy days, showering us with love and companionship.
In return, we should be there for them, especially during the times when they start to show signs of aging.