The tightness of the left neck tendon may be caused by physiological reasons such as pillow fall, or it may be caused by congenital myoclonus, muscle and other soft tissue adhesion, contracture, cervical spondylosis, fasciitis and other pathological reasons. 1. Falling pillow: due to incorrect sleeping posture or too high or too low pillow caused by the patient’s neck muscle tension, spasm, can feel the left neck tendon is very tight. 2. Congenital myoclonus: due to congenital shortening of one side of the sternocleidomastoid muscle or fibrous contracture, resulting in congenital deformity, the affected limb can appear on the left side of the neck stiffness feel a tendon tight. 3. Muscle and other soft tissue adhesion, contracture: after the healing of old traumatic tissue, local tissue adhesion, contracture, pulling the corresponding tissues, the patient may appear left neck tendon is very tight. 4. Cervical spondylosis: due to the cervical disc protruding to one side and compressing the paravertebral nerves, patients may have tightness in the left neck tendon. 5. Fasciitis: due to the neck for a long time low head caused by local fascia, ligaments and other tissues of aseptic inflammation, the patient may appear in the left neck tendon is very tight. There may be other reasons for the tightness of the left neck tendon, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment.