There are almost as many causes of back pain as there are words to describe the pain and related symptoms! Although muscle spasms are the most common cause of back pain, the spine can be susceptible to some of the same problems as other parts of your body (eg, infection). This article summarizes some of the other common and two uncommon causes of back pain.

Common Causes of Back Pain

Sprain/Strain
A sprain means an injury to a ligament, and ligaments support the spine, including its joints—the facet joints. A strain is a muscle and/or tendon injury. Tendons connect muscle to a bone. A spinal sprain or strain can happen if you fall, use poor body mechanics (eg, lifting and twisting simultaneously), during a car accident, and many other ways. These are usually quite painful and may temporarily limit movement.

Spinal Nerve Compression
When a spinal nerve root is compressed, entrapped, or pinched it becomes inflamed and starts to send messages the brain interprets as pain. In the illustration (below) of a cervical (neck) spine segment, many different disorders are causing nerve compression: a herniated disc, thickened ligament, and bone spurs (also called osteophytes).

Lumbar Herniated or Bulging Disc
A herniated disc is illustrated in the picture above. There the contents of the disc (nucleus pulposus) have spilled out through the disc’s tough protective outer layer (annulus fibrosus). The nucleus pulposus is compressing a spinal nerve root and may cause back pain, with or without leg pain. Depending on the severity of nerve compression or damage, and where in the lower back the disc herniation has occurred, the patient may develop buttock, thigh, and leg pain. The location of back pain is generally diffuse and not located in a specific area. However, leg pain typically follows specific dermatomal patterns consistent with specific nerve root irritation.

• The patient may be told they have sciatica. The term sciatica is used to describe a group of symptoms that develop when the sciatic nerve is compressed.
• True sciatica is represented by pain following a specific nerve root pattern.
• Typical lower back, buttock and proximal (nearby) thigh pain are commonly called sciatica but the sciatic nerve gives off no major braches above the knee.

Degenerative Disc Disease
This typifies many age-related spine problems. It is not really a disease but rather helps to describe the changes spinal components undergo as a result of growing older. As we grow older, our bodies undergo changes at the cellular levels. A facial wrinkle is an example of a degenerative cellular change.

As we age, the intervertebral discs begin to dehydrate (water volume diminishes); their shape and height may change affecting the space between two vertebral bodies (disc space). When disc space is reduced, a nerve passageway (neuroforamen) narrows.

The disc and facet joints work in tandem. Abnormal stresses applied to the disc are transferred to the facets resulting in overgrowth of capsular ligaments, formation of osteophytes, and reduction in facet joint movement. While all this is going on, the body is trying to find a way to stop abnormal movement, heal itself. Cartilage on the facet joints may wear away. Basically, a slow degenerative cascade develops. Bone spurs develop and may further impinge nerve roots within the foramen and or spinal canal.

Sacroiliac Joint Dysfunction
The “keystone” of the pelvis is the sacrum. Where the sacrum and the ilium meet at the left and right sides of the back are the sacroiliac (SI) joints. These joints are supported by strong ligaments. The actual amount of joint movement is very small. SI joints may move too much or not enough. When the SI joint does not function properly, the symptoms include lower back pain and proximal leg pain.

Examples of Uncommon Causes of Back Pain

Spinal infections are a less common cause of back pain. These infections can be bacterial or fungal and can affect the intervertebral discs, spinal bone (osteomyelitis), spinal cord, or area around the nerve roots (epidural space).

Spinal Tumors are benign (not cancer) or malignant (cancer). These abnormal growths (called neoplasms) can be primary or metastatic. A primary spinal tumor is one that originates in the spine—within a vertebral body, nerve roots, or spinal cord. Metastatic tumors are those that have migrated from another part of the body—such as a breast, kidney, or lung.