I recently came back to bowling after a hiatus. I love bowling again but I have an unbearable pain in my index finger right at the base of the knuckle. Is this a fit issue? Does anyone else have this problem?!
Unless you put your index finger in a finger hole, It's more likely that the pain is due to either tendonitis or arthritis. I'd go see a doctor, if I were you.
(Just to be clear, I assume by index finger you mean your "pointing' finger or the finger next to your thumb, not your middle finger.)