The trapezius muscle is an extrinsic muscle in the shoulder involved in movement of the scapula, or shoulder blade.

Position. Two in number, the trapezius muscles cover the posterior face of the neck and the posterior half of the trunk, on either side of the spine (1). Trapezius muscles connect the skeleton of the upper limbs to the skeleton of the trunk. They are part of the thoraco-appendicular muscles.

Structure. The trapezius muscle is a skeletal muscle, that is to say a muscle placed under the voluntary control of the central nervous system. It is made up of muscle fibers divided into three groups: upper, middle and lower (1).

Origin. The trapezius muscle is inserted at different points: on the medial third of the superior nuchal line, on the external occipital protuberance, on the nuchal ligament, and on the spinous processes from the cervical vertebra C7 to the thoracic vertebra T121.

Termination. The trapezius muscle is inserted at the level of the lateral third of the collarbone, as well as on the acromion and the spine of the scapula (scapula), bony protrusions of the upper edge of the scapula (1).

Innervation. The trapezius muscle is innervated:

• by the spinal root of the accessory nerve, responsible for motor skills;
• by the cervical nerves from the C3 and C4 cervical vertebrae, responsible for pain perception and proprioception (1).

Movement of the scapula, or scapula. The different muscle fibers that make up the trapezius muscle have specific functions (1):

• the upper fibers allow the shoulder blade to rise.
• the medium fibers allow the backward movement of the scapula.
• 
  the lower fibers allow the lowering of the scapula.

The upper and lower fibers work together for the rotation of the scapula, or shoulder blade.

Neck pain and back pain, pain localized respectively in the neck and back, can be linked to the trapezius muscles.

Muscle pain without lesions. (3)

• Cramp. It corresponds to an involuntary, painful and temporary contraction of a muscle such as the trapezius muscle.
• Contracture. It is an involuntary, painful and permanent contraction of a muscle such as the trapezius muscle.

Muscle injury. (3) The trapezius muscle may suffer muscle damage, accompanied by pain.

• Elongation. First stage of muscle damage, elongation corresponds to a stretching of the muscle caused by microtears and resulting in muscle disorganization.
• Breakdown. Second stage of muscle damage, the breakdown corresponds to a rupture of muscle fibers.
• Rupture. The last stage of muscle damage, it corresponds to a total rupture of a muscle.

Tendinopathies. They designate all the pathologies that can occur in tendons such as those associated with the trapezius muscle (2). The causes of these pathologies can be varied. The origin can be intrinsic as well with genetic predispositions, as extrinsic, with for example bad positions during the practice of sport.

• Tendinitis: It is an inflammation of the tendons.

Torticollis. This pathology is due to deformations or tears in the ligaments or muscles, located in the cervical vertebrae.

Drug treatments. Depending on the pathology diagnosed, certain drugs may be prescribed to reduce pain and inflammation.

Surgical treatment. Depending on the type of pathology diagnosed and its course, surgery may be necessary.

Physical treatment. Physical therapies, through specific exercise programs, can be prescribed such as physiotherapy or physiotherapy

Physical examination. First, a clinical examination is performed in order to identify and assess the symptoms perceived by the patient.

Medical imaging exams. X-ray, CT, or MRI exams can be used to confirm or deepen a diagnosis.

The right and left trapezius muscles form a trapezius, hence their name (1).