Your back is made of bones, muscles, and other tissues extending from your neck to your pelvis. Back injuries can result from sports injuries, work around the house or in the garden, or a sudden jolt such as a car accident. The lower back is the most common site of back injuries and back pain. Common back injuries include

• Sprains and strains
• Herniated disks
• Fractured (broken) vertebrae

These injuries can cause pain and limit your movement. Treatments vary but might include medicines, icing, bed rest, physical therapy, or surgery. You might be able to prevent some back injuries by maintaining a healthy weight, lifting objects with your legs, and using lower-back support when you sit.

A sprain is a stretched or torn ligament. Ligaments are tissues that connect bones at a joint. Falling, twisting, or getting hit can all cause a sprain. Ankle and wrist sprains are common. Symptoms include pain, swelling, bruising, and being unable to move your joint. You might feel a pop or tear when the injury happens.

A strain is a stretched or torn muscle or tendon. Tendons are tissues that connect muscle to bone. Twisting or pulling these tissues can cause a strain. Strains can happen suddenly or develop over time. Back and hamstring muscle strains are common. Many people get strains playing sports. Symptoms include pain, muscle spasms, swelling, and trouble moving the muscle.

At first, treatment of both sprains and strains usually involves resting the injured area, icing it, wearing a bandage or device that compresses the area, and medicines. Later treatment might include exercise and physical therapy.

Your backbone, or spine, is made up of 26 bones called vertebrae. In between them are soft disks filled with a jelly-like substance. These disks cushion the vertebrae and keep them in place. As you age, the disks break down or degenerate. As they do, they lose their cushioning ability. This can lead to pain if the back is stressed.

A herniated disk is a disk that ruptures. This allows the jelly-like center of the disk to leak, irritating the nearby nerves. This can cause sciatica or back pain.

Your doctor will diagnose a herniated disk with a physical exam and, sometimes, imaging tests. With treatment, most people recover. Treatments include rest, pain and anti-inflammatory medicines, physical therapy, and sometimes surgery.

Intervertebral Discs and Ligaments of the Vertebral Column

The bodies of adjacent vertebrae are strongly anchored to each other by an intervertebral disc. This structure provides padding between the bones during weight bearing, and because it can change shape, also allows for movement between the vertebrae. Although the total amount of movement available between any two adjacent vertebrae is small, when these movements are summed together along the entire length of the vertebral column, large body movements can be produced. Ligaments that extend along the length of the vertebral column also contribute to its overall support and stability.

Intervertebral Disc. The bodies of adjacent vertebrae are separated and united by an intervertebral disc, which provides padding and allows for movements between adjacent vertebrae. The disc consists of a fibrous outer layer called the anulus fibrosus and a gel-like center called the nucleus pulposus. The intervertebral foramen is the opening formed between adjacent vertebrae for the exit of a spinal nerve.

Amphiarthrosis

An amphiarthrosis is a joint that has limited mobility. An example of this type of joint is the cartilaginous joint that unites the bodies of adjacent vertebrae. Filling the gap between the vertebrae is a thick pad of fibrocartilage called an intervertebral disc. Each intervertebral disc strongly unites the vertebrae but still allows for a limited amount of movement between them. However, the small movements available between adjacent vertebrae can sum together along the length of the vertebral column to provide for large ranges of body movements.

Another example of an amphiarthrosis is the pubic symphysis of the pelvis. This is a cartilaginous joint in which the pubic regions of the right and left hip bones are strongly anchored to each other by fibrocartilage. This joint normally has very little mobility. The strength of the pubic symphysis is important in conferring weight-bearing stability to the pelvis.

Intervertebral Disc

An intervertebral disc is a fibrocartilaginous pad that fills the gap between adjacent vertebral bodies (see image). Each disc is anchored to the bodies of its adjacent vertebrae, thus strongly uniting these. The discs also provide padding between vertebrae during weight bearing. Because of this, intervertebral discs are thin in the cervical region and thickest in the lumbar region, which carries the most body weight. In total, the intervertebral discs account for approximately 25 percent of your body height between the top of the pelvis and the base of the skull. Intervertebral discs are also flexible and can change shape to allow for movements of the vertebral column.

Each intervertebral disc consists of two parts. The anulus fibrosus is the tough, fibrous outer layer of the disc. It forms a circle (anulus = “ring” or “circle”) and is firmly anchored to the outer margins of the adjacent vertebral bodies. Inside is the nucleus pulposus, consisting of a softer, more gel-like material. It has a high water content that serves to resist compression and thus is important for weight bearing. With increasing age, the water content of the nucleus pulposus gradually declines. This causes the disc to become thinner, decreasing total body height somewhat, and reduces the flexibility and range of motion of the disc, making bending more difficult.

The gel-like nature of the nucleus pulposus also allows the intervertebral disc to change shape as one vertebra rocks side to side or forward and back in relation to its neighbors during movements of the vertebral column. Thus, bending forward causes compression of the anterior portion of the disc but expansion of the posterior disc. If the posterior anulus fibrosus is weakened due to injury or increasing age, the pressure exerted on the disc when bending forward and lifting a heavy object can cause the nucleus pulposus to protrude posteriorly through the anulus fibrosus, resulting in a herniated disc (“ruptured” or “slipped” disc) (image). The posterior bulging of the nucleus pulposus can cause compression of a spinal nerve at the point where it exits through the intervertebral foramen, with resulting pain and/or muscle weakness in those body regions supplied by that nerve. The most common sites for disc herniation are the L4/L5 or L5/S1 intervertebral discs, which can cause sciatica, a widespread pain that radiates from the lower back down the thigh and into the leg. Similar injuries of the C5/C6 or C6/C7 intervertebral discs, following forcible hyperflexion of the neck from a collision accident or football injury, can produce pain in the neck, shoulder, and upper limb.

Ligaments of the Vertebral Column

Adjacent vertebrae are united by ligaments that run the length of the vertebral column along both its posterior and anterior aspects (image). These serve to resist excess forward or backward bending movements of the vertebral column, respectively.

The anterior longitudinal ligament runs down the anterior side of the entire vertebral column, uniting the vertebral bodies. It serves to resist excess backward bending of the vertebral column. Protection against this movement is particularly important in the neck, where extreme posterior bending of the head and neck can stretch or tear this ligament, resulting in a painful whiplash injury. Prior to the mandatory installation of seat headrests, whiplash injuries were common for passengers involved in a rear-end automobile collision.

The supraspinous ligament is located on the posterior side of the vertebral column, where it interconnects the spinous processes of the thoracic and lumbar vertebrae. This strong ligament supports the vertebral column during forward bending motions. In the posterior neck, where the cervical spinous processes are short, the supraspinous ligament expands to become the nuchal ligament (nuchae = “nape” or “back of the neck”). The nuchal ligament is attached to the cervical spinous processes and extends upward and posteriorly to attach to the midline base of the skull, out to the external occipital protuberance. It supports the skull and prevents it from falling forward. This ligament is much larger and stronger in four-legged animals such as cows, where the large skull hangs off the front end of the vertebral column. You can easily feel this ligament by first extending your head backward and pressing down on the posterior midline of your neck. Then tilt your head forward and you will fill the nuchal ligament popping out as it tightens to limit anterior bending of the head and neck.

Additional ligaments are located inside the vertebral canal, next to the spinal cord, along the length of the vertebral column. The posterior longitudinal ligament is found anterior to the spinal cord, where it is attached to the posterior sides of the vertebral bodies. Posterior to the spinal cord is the ligamentum flavum (“yellow ligament”). This consists of a series of short, paired ligaments, each of which interconnects the lamina regions of adjacent vertebrae. The ligamentum flavum has large numbers of elastic fibers, which have a yellowish color, allowing it to stretch and then pull back. Both of these ligaments provide important support for the vertebral column when bending forward.

Vertebral compression fractures (VCFs) of the spinal column occur secondary to an axial/compressive (and to a lesser extent, flexion) load with resultant biomechanical failure of the bone resulting in a fracture. VCFs by definition compromise the anterior column of the spine, thereby resulting in compromise to the anterior half of the vertebral body (VB) and the anterior longitudinal ligament (ALL). This leads to the characteristic wedge-shaped deformity.

VCFs do not involve the posterior half of the VB and do not involve the posterior osseous components or the posterior ligamentous complex (PLC). The former distinguishes a compression fracture from a burst fracture. The implications of these compression fractures are related to the stability of the resulting structure and potential for deformity progression. Compression fractures are usually considered stable and do not require surgical instrumentation.

Spinal fusion is used to strengthen the spine and prevent painful movements in people with degenerative disc disease or spondylolisthesis (following laminectomy). The spinal disc between two or more vertebrae is removed and the adjacent vertebrae are “fused” by bone grafts and/or metal devices secured by screws. Spinal fusion may result in some loss of flexibility in the spine and requires a long recovery period to allow the bone grafts to grow and fuse the vertebrae together. Spinal fusion has been associated with an acceleration of disc degeneration at adjacent levels of the spine.

Spinal stenosis happens when the spaces in the spine narrow and create pressure on the spinal cord and nerve roots. The spinal cord is a bundle of nerves that comes out of the base of the brain and runs down the center of the spine. The nerve roots branch out from the cord. The narrowing usually occurs over time and involves one or more areas of the spine:

• The spinal canal, the hollow space in the center of each vertebrae (bones in the spine that protect the spinal cord); the spinal cord and nerve roots run through the spinal canal.
• The space at the base or roots of nerves branching out from the spinal cord.
• The openings between vertebrae, through which nerves leave the spine and go to other parts of the body.

There are many different structures in the anatomy of the back that work together to support your body. There are four regions of the spine:

• Cervical spine.
• Thoracic spine.
• Lumbar spine.
• Sacrum and coccyx.

Spinal stenosis most commonly develops in the lumbar spine and cervical spine.

If you have had lower back pain, you are not alone. Back pain is one of most common reasons people see a doctor or miss days at work. Even school-age children can have back pain.

Back pain can range in intensity from a dull, constant ache to a sudden, sharp or shooting pain. It can begin suddenly as a result of an accident or by lifting something heavy, or it can develop over time as we age. Getting too little exercise followed by a strenuous workout also can cause back pain.

There are two types of back pain:

• Acute, or short-term back pain lasts a few days to a few weeks. Most low back pain is acute. It tends to resolve on its own within a few days with self-care and there is no residual loss of function. In some cases a few months are required for the symptoms to disappear.
• Chronic back pain is defined as pain that continues for 12 weeks or longer, even after an initial injury or underlying cause of acute low back pain has been treated. About 20 percent of people affected by acute low back pain develop chronic low back pain with persistent symptoms at one year. Even if pain persists, it does not always mean there is a medically serious underlying cause or one that can be easily identified and treated. In some cases, treatment successfully relieves chronic low back pain, but in other cases pain continues despite medical and surgical treatment.

Back pain is one of the most common medical problems in the United States. It can range from a dull, constant ache to a sudden, sharp pain. Sometimes it can come on suddenly – from an accident, a fall, or lifting something heavy, or it can develop slowly because of age-related degenerative changes to the spine. In some cases, inflammatory disorders or other medical conditions cause back pain.

Treatment varies depending on the cause and symptoms; however, there are steps you can take to improve your health and lower your chance of developing chronic or long-lasting back pain.

Understanding the Anatomy of the Back

There are many different structures in the anatomy of the back that work together to support your body. Problems with any one of these structures can cause back pain.

• There are four regions of the spine:
  • Cervical spine.
  • Thoracic spine.
  • Lumbar spine.
  • Sacrum and coccyx.

• Parts of the spine and back include:
  • Vertebrae – small bones stacked on top of one another, which protect the spinal cord.
  • Spinal cord – long bundle of nerves that run down the back through a canal in the vertebrae.
  • Intervertebral discs – cushion-like pads between the vertebrae that act like shock absorbers and spacers for the spine.
  • Ligaments – short bands of tough, flexible tissue that hold the vertebrae in place.
  • Tendons – cord of tissue that connects muscle to bone.
  • Muscles – a bundle of dynamic fibers that support your spine and upper body and help you move.

Back pain is one of most common reasons people see a doctor or miss days at work. Back pain can range in intensity from a dull, constant ache to a sudden, sharp or shooting pain. There are two types of back pain:

• Acute (short-term) back pain lasts a few days to a few weeks. It usually resolves on its own within a few days with self-care and there is no long-term loss of function.
• Chronic back pain is pain that continues for 12 weeks or longer, even after an initial injury or underlying cause of back pain has been treated.

Risk factors for low back pain

• Age: The first attack of low back pain typically occurs between the ages of 30 and 50 and may become more common as you age.
• Fitness level: Back pain is more common among people who are not physically fit, as their muscles may not properly support the spine.
• Weight gain: Being overweight, obese, or quickly gaining significant amounts of weight can put stress on your back and cause pain.
• Genetics: Some causes of back pain, such as ankylosing spondylitis (a form of arthritis that affects the spine), have a genetic component.
• Job-related factors: Job that requires heavy lifting, pushing or pulling, or twisting or vibrating the spine can injure your back, as can sitting at a desk all day, especially if you have poor posture or sit in a chair with not enough back support.
• Mental health: Anxiety, mood, and depression can influence how you perceive your back pain and stress can cause muscle tension.
• Smoking: This can restrict blood flow and oxygen to your discs, causing them to degenerate faster.
• Backpack overload in children: A backpack overloaded with schoolbooks and supplies can strain the back and cause muscle fatigue.

Recommendations for keeping your back healthy

• Avoid movements that jolt or strain your back.
• Exercise regularly to keep your muscles strong and flexible. Consult a physician for a list of low-impact, age-appropriate exercises that are specifically targeted to strengthening lower back and abdominal muscles.
• Maintain a healthy weight and eat a nutritious diet that promotes new bone growth.
• Use ergonomically designed furniture and equipment at home and at work.
• Switch sitting positions often and periodically walk around the office or gently stretch your muscles to relieve tension. Put your feet on a low stool or a stack of books when sitting for a long time.
• Wear comfortable, low-heeled shoes.
• Sleeping on your side with your knees drawn up in a fetal position can help open up the joints in the spine and relieve pressure by reducing the curvature of the spine. Always sleep on a firm surface.    
• Don't try to lift objects that are too heavy. Lift from the knees, keep a straight back, and objects close to the body.    
• Quit smoking. Smoking reduces blood flow to the lower spine, which can contribute to spinal disc degeneration. Smoking also increases the risk of osteoporosis and impedes healing. Coughing due to heavy smoking also may cause back pain.

Discectomy and microdiscectomy involve removing a herniated disc through an incision in the back (microdiscectomy uses a much smaller incision in the back and allows for a more rapid recovery). Laminectomy and discectomy are frequently performed together and the combination is one of the more common ways to remove pressure on a nerve root from a herniated disc or bone spur.