The pain in the left tendon of the neck may be caused by muscle strain, falling pillow, cervical spondylosis and so on. 1. Muscle strain: when the patient due to strenuous exercise, or excessive fatigue caused by neck muscle strain, can appear in the left side of the neck tendon pain. 2. Falling pillow: due to sleeping for a long time to maintain a position, and the pillow height is not appropriate, resulting in patients with falling pillow. 3. Cervical spondylosis: due to abnormal curvature of the cervical spine, or cervical spine degenerative disease, etc., it will compress or stimulate the nerves, and then the left side of the neck tendon pain occurs. It is recommended that patients with pain in the left side of the neck tendon reduce activities, and at the same time timely medical care, under the guidance of the doctor to clearly diagnose the causes of the symptoms, and targeted treatment.