When your upper back (thoracic spine) or pelvis gets stiff or out of balance, it causes your shoulders to roll forward and inward.
This puts extra tension on your neck and shoulder muscles, which can make them feel tight or uncomfortable.
That’s what many people call shoulder stiffness.If your body stays out of alignment for too long, that tightness can turn into real pain.
You might start to lose neck movement, feel stronger tension in your shoulders, or even notice numbness in some cases.