My daughter in law, with mild scoliosis, uses topical Diclofenac for pain. She is a nurse practitioner, so she knows her meds, and her work has put stress on her back so she has had to deal with the pain. She likes the topical analgesics because they bypass your stomach and reduce those issues with stomach irritation.
Diclofenac is the main ingredient in Voltaren. You can get this OTC in most pharmacies and some groceries.
Voltaren Active Ingredients: Diclofenac sodium (NSAID†) 1% (equivalent to 0.93% diclofenac) - Arthritis pain reliever. Nonsteroidal anti-inflammatory drug.