Thanks, Everyone. 
Nerys Ghemor, if you're in a state that licenses massage therapists, the licensing board is who they're accountable to. All the ones I've been to have all been very careful about modesty. Standard procedure is to keep the client covered by a sheet or blanket, except for whichever body part they're working on at the moment. As far as the health concern, if I were in your position, I would just tell the therapist about my wonky back. Most massage techniques are gentle and unlikely to cause problems. The only reason I was concerned this time was that my body is obviously still healing from all the surgery.

Nerys Ghemor, if you're in a state that licenses massage therapists, the licensing board is who they're accountable to. All the ones I've been to have all been very careful about modesty. Standard procedure is to keep the client covered by a sheet or blanket, except for whichever body part they're working on at the moment. As far as the health concern, if I were in your position, I would just tell the therapist about my wonky back. Most massage techniques are gentle and unlikely to cause problems. The only reason I was concerned this time was that my body is obviously still healing from all the surgery.