If your talking about just inside the shoulder blades then I feel your pain.
Rolling on a very hard foam or PVC roller helps squash the knot but isnt pleasant feeling.
Acupuncture works. As does accupressure.
It sucks. Mine used to get so bad it would throw off my thorasic spine slightly and i would be leaning over a chair or something every 5 minutes all day long to crack my back.
Its under contorl alot more now. Having my wife walk on my back daily helps.