So what do you do? Get advice from Tony Jackson is what. He recommends using an offset syringe to inject glue between the surfaces of the joint, drilling a careful hole first.
He doesn't use a needle, but before he told me this I'd bought one from my local chemist. It's not possible to fill the syringe with wood glue through the needle; but if you fill it, then add the needle, the glue will come out all right. This is good, as you can get glue deep into small cracks.
It's a delicate job. I'm sure experience helps, but alas I have none.