Cervical spine instability is divided into upper cervical instability and lower cervical instability. The human cervical spine has a total of seven vertebrae, the first and second cervical vertebrae together are called the upper cervical vertebrae, and the third to seventh cervical vertebrae together are called the lower cervical vertebrae. The first and second cervical vertebrae have special names in medicine, called atlas and cardinal vertebrae, respectively. Cervical instability is the degeneration of the cervical spine and chronic strain damage, so that the stable structure of the cervical spine is destroyed, which leads to the movement of each vertebra in excess of its original range of motion, resulting in a series of painful and uncomfortable symptoms in the neck and shoulders. Upper cervical instability is mainly due to congenital deformity, trauma, inflammation and other factors that cause the atlanto-occipital joint and atlanto-axial joint to lose their normal alignment relationship, resulting in a series of clinical manifestations caused by pressure on the spinal cord and nerves. When the upper cervical spine is unstable, the atlantoaxial spine can produce forward, backward or rotational dislocation, causing pressure on the spinal cord above the neck, which may lead to tetraplegia or even respiratory muscle paralysis and death of the patient. Therefore, upper cervical instability must be diagnosed and treated promptly. Lower cervical instability is defined as below cervical segment 2 to 3, where the range of motion of the cervical vertebrae exceeds the original physiological range, mainly caused by cervical degeneration and trauma. Cervical instability is usually diagnosed by taking a cervical spine dynamic radiograph. Cervical instability can be diagnosed if a vertebral body is displaced forward or backward by more than 3.5 mm or the angle difference between adjacent vertebral bodies is greater than 11° on radiographs compared to its adjacent vertebral bodies. Upper and lower cervical instability is more common in clinical practice, but the clinical symptoms vary greatly, from no symptoms, mild neck discomfort to radiating pain in the upper extremities, and then more serious, which may lead to paralysis, the severity of symptoms depends mainly on the degree of spinal cord and nerve compression, the heavier the compression, the more severe the symptoms. Therefore, if lower cervical instability occurs, it is important to consult a specialist on how to treat it, and not to blindly carry out some incorrect treatment to avoid delaying the condition.