Neck can not be twisted from side to side, may be caused by pillow, cervical spondylosis, cervical fasciitis, ankylosing spondylitis and other reasons. 1. Pillow fall: pillow fall, also known as loss of pillow, is a kind of disease characterized by stiffness of neck muscles, pain, and limitation of movement in the morning, which may be caused by poor sleeping posture, improper pillow height, etc., and may lead to the patient’s neck not being able to twist from side to side. 2. Cervical spondylosis: cervical spondylosis mainly includes cervical vertebrae degeneration, hyperplasia, cervical intervertebral disc protrusion, etc., and its main clinical manifestations are head and neck pain, stiffness, and activity limitation, etc., and the patient’s inability to twist his neck from side to side may be caused by cervical spondylosis. 3. Cervical Fasciitis: Cervical Fasciitis is a kind of aseptic inflammation of the muscle fascia and muscle tissues of the neck due to various reasons, which is mainly manifested as neck and shoulder pain, numbness, stiffness, and activity limitation. 4. Ankylosing spondylitis: Ankylosing spondylitis is a chronic inflammatory disease caused by a combination of genetic or environmental factors that can involve the entire spine, hip joints, sacroiliac joints, etc., resulting in pain and limited activities, and when it involves the cervical vertebrae, it can lead to unfavorable cervical vertebrae activities, unable to flexion, extension and twisting normally. It is recommended that patients seek timely medical examination to clarify the cause of the disease and then carry out targeted treatment, pay attention to rest in life, correct bad posture, and regular review.