Sore back

["guest@endurance.net" <guest@endurance.net>]

Angie Given agiven@coair.com
What are the indications that a horse is suffering from a sore back?  I've just recently purchased a lightweight saddle.  It seems to be working fine, but with my gelding dropping pounds and his build ever-changing during conditioning, I want to keep an eye out for problems that may or may not occur.  His withers are becoming more prominent and his belly shrinking, so adjustments are being made to the saddle fit on a regular basis.  Thanks for any advice you have to offer