on (one's) pins
On one's legs; standing. Typically used when pointing out that one is not able to stand very steadily. I was a bit wobbly on my pins for a few days after the surgery, but aside from that I didn't have many side effects. You can see that she's shakier on her pins than she was at the peak of her career.
on your ˈpins
(old-fashioned, informal) on your legs; when standing up or walking: He’s not as steady on his pins as he used to be. I worry about him going out.