Do dogs know that medicine helps them?

[Smokeycat]

Kryten really seems to know that his Cartrophen injections help him walk pain free. He gets his injection on the 20th of each month and it appears to work completely for 30 days. There is some limping on the last day of the cycles that have 31 days.
What makes me think he knows that the injection is what helps him is his reaction when I get the Cartrophen out of the fridge. He perks up and comes to lay next to the counter while I prepare the syringe. I call his name and he stands and positions his neck so that it is aligned for an easy injection, which given his reaction he doesn't even feel (I know he must). He then smiles when I put his collar back on and this dog typically only smiles when excited as his happy face looks mopey.
Has anyone else seen this sort of behavior? Some of it might be unintentional training as he has been getting the monthly injections for a year now but that doesn't seem to explain why he is happy to see the injection stuff come out.

 

[Jakesmum]

I think that they must know what makes them feel better. When I give Jake his bath he will grudgingly walk into the bathroom and get his front paws in the tub, after I give him a dilute bleach rinse at the advice of the dermatologist and he lifts his back legs up like he's peeing so I can get them really good, he always feels so much better after a bath and his rinse.

 

[Nik]

How fast is the injection suppose to help with the pain? If the effect is pretty quick then he could definitely be associating the lack of pain with the injection.

In any case I believe that they are pretty smart and know much more then they (typically) get credit for.

 

[Smokeycat]

How fast is the injection suppose to help with the pain? If the effect is pretty quick then he could definitely be associating the lack of pain with the injection.

In any case I believe that they are pretty smart and know much more then they (typically) get credit for.

It's not actually a pain reliever. It's more like synthetic glucosamine. It supposed to support joint function by increasing the production of joint fluid while preventing further breakdown of the cartilage. It also is supposed to support blood flow to the joints. A side effect is less inflammation and therefore less pain.