Maybe, maybe not: muzzle brakes do reduce recoil substantially...but the tradeoff is in increased damage to hearing if you forget your hearing protection for a shot, like at hunting, or when resuming fire after a ceasefire target change. Also, they have a modest price bump, and on non-threaded barrels require a smith to machine, making your piece no longer 'stock'. It's not always better, but it is another option available!
Shoulder injuries? I'd look at doing everything:
-a "tank/sail" style muzzle brake (looks like a giant sail to catch the 'wind' of the gases, pulling the gun forward, or at least slowing it down)
-Limbsaver buttpad, these are worth every penny IMO!
-PAST device mentioned earlier
-add a lead weight of perhaps one pound, or even two, secured into the buttstock (slows initial recoil acceleration, taking the 'bite' out of the recoil)
Doing all of that should help save your shoulder and muscles...no sense doing more damage to yourself!
Notice they are now selling bolt-gun stocks that have a recoil absorbing spring system, much like their shotgun products: Browse around this site, might be more you can try:
http://www.nokick.com/Knoxx_Stocks_s/80.htm
http://www.blackhawk.com/catalog/Rifle-Stocks,166.htm
http://www.blackhawk.com/product/Rifle-CompStock,218,166.htm
http://www.blackhawk.com/product/Axiom-TH-Thumbhole-Rifle-Stock,1526,166.htm
http://www.blackhawk.com/product/Axiom-VS-Rifle-Stock,219,166.htm
