Is it time that we consider putting my moms dog to sleep?

My mom has a 12 year old pit bull. He's had arthritis in his front paws for a while. We give him medication everyday, but he continues to limp. Mostly up the stairs. He has arthritis in his spine too. The vet told us to hot compress his spine multiple times a day. That was two months ago, but a few days ago, he started whining, growling, and yelping. Sometimes barking too. I'm pretty positive it's his arthritis. I took him for a 10 minute walk today, and when we came back, he was limping up the stairs, then his back legs gave out, and he fell down the stairs. I sort of have to lift him up the stairs and pick him up onto the bed. I've been thinking that the time to put him to sleep is approaching. I haven't flat out said it to my mom, but I know she's thinking it. Neither of us want him to suffer.

Is it time that we consider putting my moms dog to sleep?
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