The left shoulder with the left neck for the left side of the neck and shoulder area, the left side of the neck and shoulder area of the soreness of many reasons, common cervical disc herniation, frozen shoulder and muscle strain. 1. Cervical disc herniation: degenerative changes in the cervical disc cause the fibrous ring of the cervical disc to fracture at the back side of the cervical disc, and the nucleus pulposus tissue protrudes into the spinal canal, stimulating the surrounding nerves and blood vessels. If the left nerve root is compressed, it can cause pain in the left side of the neck and shoulder. 2. Frozen shoulder: Chronic inflammation and fibrosis of the joint capsule and surrounding ligamentous tissues lead to decreased elasticity of the soft tissues, resulting in soreness and limitation of activities around the shoulder and neck. 3. Muscle strain: prolonged stooping and bending of the head and other bad postures lead to muscle tension in the neck and shoulder area, and repeated muscle pulling and stimulation lead to neck and shoulder soreness. The left side of the neck and shoulder pain may have other reasons such as cold, etc., should go to the hospital in time, improve the examination to clarify the cause of the disease, and standardized treatment under the guidance of the doctor.