Although is looks like one big muscle shaped like a trapezoid, when we talk about it’s function, we refer to it as 3 distinct muscles (see red lines). It runs from the occiput of the skull to half way down the thoracic spine.
A simplified anatomy explanation: The upper fibers raise the scapula (shoulder blade) and extend the neck. The middle fibers retract the scapula (think about a row). The lower fibers lower the scapula. Often times, there is an imbalance and the upper fibers are stronger than the lower fibers, causing malposition of the scapula and shoulder pain and instability.
This is one of the reasons why when someone presents with neck pain, it helps to treat the upper back. And when someone has pain in the shoulders, we also have to look towards the neck.
This muscle has big trigger points at the top of the shoulder that can refer strong headaches, especially for computer workers.
It is necessary to take a full body approach to treatment in order to create more permanent, lasting results. When a joint in the spine is stuck, it irritates the nerves and causes the surrounding muscles to spasm. The chiropractic adjustment releases this tension and enables the muscle to relax. Combined with specific exercises to correct postural changes, you will feel a relief of pain in the shoulders.