Question
I have been having tight muscles from my shoulder to my spinal cord, the muscles tighten up so bad, been to physical therapy, didn't help, went to therapy message, able to get some relief for a few days, muscles begin to tighten up again, now can't lift left arm up high, it feels like if something would pop, it would feel better, muscles will tighten in arm down to elbow and you can feel big knots, will release and radiate back up to top of should and muscles become tight again.  No injury, when this began, thought it was from mattress, taking ibuprofen but stay in pain, arm now has a dull throbbing feeling for a while and will ease for a while. No diabetic, no heart disease.

Answer
it sounds like you have nerve involvement and that is why the physical therapy didn't help. you may have muscles pulling the spine out of place and then causing pinched nerves in the spine. the nerves in the spine control all your muscles and the sensation (throbbing pain) in your arms. Its called the brachial plexus. Try googling it.
If the pt was temporary relief you need to have a chiropractor or massage therapist deal with the tight muscles , but more importantly have the spine re-aligned to remove pressure off the nerves. again, the nerves control your muscles. If you have nerve pressure then you will have tight muscles and pain radiating into the arm.