I think I am right in beliving the brain tells us we feel pain via the nerves.

I am taking Gabapentin for neuropathy and the pains have decreased sufficiently that I am no longer in agony.
The Gabapentin works by blocking the parts of my brain that tell me I have pain, I hope I am right so far..

If this is right then why can`t the meds stop all the other pains I have?

I have rotor cuff injury having steroid injections to ease the inflamation so why can`t the Gabapentin block the pain signals from the nerves in my shoulder at the same time?

Anybody got the answer?