She should NOT be, doing child care, alone, in her condition.
It is for her safety and your child's.
It is, common sense.
She is 'normal.' She just has health concerns. Which affect her and her mobility. So you teach your child that & her.
You teach her as well.... and you be a Mom, and keep your child safe.
If something should happen, to your son or her... while they are alone together... you will not forgive yourself.
I know many Elderly Grandparents. They have health concerns. They have a hard time, keeping up with their young Grandchildren.
Even driving around can be hard for them, much less, keeping up with them at home. Kids are, active.
The Physical aspect.... IS VERY IMPORTANT.
I know a Grandparent, that while watching his Grandchild, all of a sudden fell down. Why? Because he fainted. He was outside in the yard with his Grandchild. He hit his head. Could not get up. Had to be rushed to the hospital. Good thing, his wife was home, too. Otherwise, his Young toddler Grandchild, would be without supervision or worse. Can you imagine, what could have happened- to the child and to him???? If his Wife was not home with them????? The Grandchild's parents were not home of course, they were at work. If his Wife was not home, then he'd still be laying on the ground outside passed out, and the Grandchild unsupervised for HOURS. Who knows, what could have happened then.
So keep that in mind.
When a Grandparent is disabled and/or with health problems... there has to be another Adult person there as well. Watching the child. ie: a Buddy system. For just in case. You CANNOT predict, scenarios.
I'm sorry, but you should not leave your child alone with her to Babysit.... at all. Not in her condition.
It is all about safety for your child and her's.
She is not physically able.
Is her home baby-proofed or safety proofed???? That is another concern. You should do that for her, or your Husband.
Don't compare her to all the other Grandmas you see out and about.
This is your Mom. Arthritis... is very disabling and painful and crippling.
It just is.
I hope she is seeing a Doctor for her Arthritis.
All the best,
Susan