A complicated system of ligaments and muscles serves to control movement, maintain posture, and support the lower back and pelvis. Ligaments are fibrous bands of soft tissue that attach a bone to another bone. The ligamentous system of the spine protects the intervertebral discs from injury, and prevents excessive movement of the spine The muscular system of the lower back is complex, and includes the deep erector spinae or paraspinal muscle groups that run parallel to the spine. In addition there are larger and more superficial muscles that help to move and protect the lower back. The larger superficial muscles help move and stabilize the lower back. The deeper spinal muscles can be multisegmental connecting and attaching to more than one vertebra or muscles that support, stabilize and move one segment in relation to another. When thoracic 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. Injury to the thoracic spine causing weakness or tightness of the muscles or laxity of the ligaments of the lower back can result in pain, decreased ability to maintain good posture, limitation in movement and instability of the back.