One of his big toes has been bothering him for quite some time. It was from an old sports injury, and the doctor suggested that John takes care of it before it hurts him further.
From what I understand the doc is going to cut John's toe open, shaved off a bit of his bone, and place a little metal stick in the bone.
Poor thing. At least the surgery will help John wiggle his big toe and walk better and pain-free.