What Is the Trapezius Muscle? Trapezius muscles are large, paired, triangular muscles in the back of your neck and upper back. They extend down your back, but they’re mostly involved in the movements ...

The trapezius muscle starts right below the skull, runs down the neck and across the shoulders, and then continues down the spine in a “V” shape. It works to stabilize your shoulders and upper back.

If you’ve got a lump on top of your shoulder muscle, you have a good chance of it being a trapezius knot. This type of lump in the trapezius muscle — called a myofascial trigger point — is among the ...