A complicated system of ligaments and muscles serves to control movement, maintain posture, and support the head and neck. Ligaments are fibrous bands of soft tissue that attach bone to bone. The ligamentous system of the spine protects the intervertebral discs and spine from injury, and prevents excessive movement of the head and neck. The muscular system of the cervical spine is complex, and includes the deep erector spinae or paraspinal muscle groups that run parallel to the spine. There are also larger and more superficial muscles that help to move and protect the neck and head. When neck or spinal motion is pushed to the extreme, such as in a car accident or whiplash injury, these ligaments and muscles can be damaged. Ligament damage sprain and muscle damage strain can produce pain, soreness, loss of motion, and, if severe enough, joint instability. Irritation or injury of the structures of the spine may produce spasm and pain of the muscles of the head and neck. This can cause symptoms that radiate into the arms and hands.