Cat not retracting claw

[GinAndOnIt]

But just the one claw on one foot - the others seem to retract fine.

I originally thought it was just getting long, but DP said it was unusual for only one claw to be long, and having had a bit of a press of his feet, it does seem that one is just permanently out.

He is knocking on a bit - he's 11. We rescued him in March. He doesn't seem in pain with it, but just wondering if this is common in older cats, and whether it needs treatment or to be trimmed?

I take it you've tried to (very very gently) see if the claw will go back in?

Unretractable claws can be a little problematic. I'd vet him. (You'll likely get a general checkup at the same time if your vet is anything like ours.)