Exploring the trapezius muscle
I’m not sure that there is any muscle as deeply integrated with the movement of the scapula as the trapezius muscle. Since it’s a large muscle with multiple fiber directions and actions, we commonly divide it into three sections to describe it more clearly.
The three sections are:
- The upper trapezius
- The middle trapezius
- The lower trapezius
What does trapezius mean?
The name trapezius comes from the Greek word “trapeza”, which means four-sided. So, you can see that trapezius is named for its shape. When the left and right sides are paired, they form a trapezium. The trapezius composes the superficial layer of muscle on the back, and is only partly covered by the large latissimus dorsi muscle.
Where does the trapezius muscle attach?
Origin of trapezius
Each of the sections of the trapezius originates on different locations on the body. The upper trapezius originates on the base of the occiput, the ligamentum nuchae, and the spinous processes of vertebrae C1-C7. You’ll find that the middle trapezius originates on the spinous processes of C7 – T3, while the lower trapezius originates on the spinous processes of T4 – T12.
Insertion of trapezius
Just like the origins, each section of the trapezius inserts on different places in the body. The upper trapezius inserts on the lateral clavicle and the acromion process. However, both the middle and lower trapezius insert on the spine of the scapula.
What actions does the trapezius muscle do?
All three sections of the trapezius work together to upwardly rotate the scapula. This is possible because of the points of insertion. It helps to imagine a central point around which the scapula rotates and see that the muscular attachments are like ropes on a pulley.
In addition to their common action, you’ll find that each of the sections of this muscle also does an action which is unique to that section. The upper trapezius elevates, or lifts the scapula. In the middle section, trapezius retracts the scapulae, or moves them toward the spine. Finally, the lower trapezius depresses, or lowers the scapula.
What are the most common injuries to the trapezius?
The most common cause of pain in the trapezius is STRESS! Many people seem to carry their stress around in their shoulders. It’s not uncommon for the upper trapezius to be involved in headaches and torticollis (wry neck/waking up with a stiff neck). Additionally, trigger points in the trapezius can be particularly nasty and contribute to the headaches that are so common.