6 Causes of Mechanical Back Pain
The cause of most back and neck pain is mechanical—meaning the source of the pain may be triggered by the movements of the spine. The moving parts of the spinal column include ligaments, tendons, muscles, intervertebral discs, vertebral bodies, and facet joints.
- A common region for mechanical low back pain is the lumbar spine (L1-L5). These 5 levels absorb and distribute most of the body’s weight during static and active movement. Static means the body is stationary (eg, standing) but not actively moving (eg, walking).
- The neck is the most mobile section of the spinal column. Here, 7 cervical vertebrae, which are much smaller than the lumbar vertebral bodies, support the weight of the head (average 10 pounds). The diversity of cervical motion includes nodding, bending forward, backward, and side to side.
However, even if the body is not moving, parts of the anatomy continue to support the spine (eg, ligaments). Whether static or active, there are different mechanical forces at play—such as gravity, tension, compression, and stress—that increase and decrease. So, the spine is always at work balancing these effects to help prevent injury.
#1. Back or Neck Sprain and Strain
A back or neck sprain occurs when a spinal ligament (bands of strong tissues that hold bones together) is overstretched or torn. In contrast, back or neck strain involves a muscle and/or tendon attachment. In can be difficult to identify the source of the pain. Whether you sprain or strain your back (or neck), the soft tissues are injured and react by swelling, thus causing pain. Affected muscles may go into spasm that can be very painful. Stiffness is another symptom that may make movement difficult.
#2. Disc Herniation
Intervertebral discs separate the drum-shaped vertebral bodies. Each disc is anchored into place by endplates; a fibrous connective tissue that is part of the disc. Discs are made of fibrocartilage and allow a small amount of movement at each vertebral segment (2 vertebrae and one disc). The disc’s outer ring (annulus fibrosis) protects the inner gel-like center (nucleus pulposus).
Disc herniation occurs when the gel-like material breaks through the outer ring, often causing nerve compression, irritation, inflammation, and pain. Pain may radiate (travel) into an arm or leg, depending on where in the spine the herniation occurs. Numbness, weakness, and tingling sensations may accompany pain. A disc may rupture in different directions: front (anterior), back (posterior), and/or side (lateral).
#3. Vertebral Compression Fracture (VCF)
A vertebral compression fracture occurs when force causes a vertebral body to collapse. Trauma (eg, fall) is a cause, although VCF is often associated with osteoporosis, a disease-causing loss of bone mineral density and strength. In people with osteoporosis, a VCF can occur spontaneously such as during lifting or bending forward. These fractures usually cause sudden and severe pain.
#4. Lumbar Spinal Stenosis (LSS)
Spinal stenosis in the low back develops when nerve root passageways and/or the spinal canal narrow. The term stenosis means narrow. When nerve structures are compressed the dominate symptom is pain; and pain can radiate into one or both legs (sciatica). LSS usually affects older adults and can be associated with degenerative changes that cause bone and/or tissue to grow into nerve pathways or compress the spinal canal.
#5. Spinal Osteoarthritis (Spondylosis)
Spondylosis is the medical term for degenerative spinal osteoarthritis; common in older adults. Similar to other types of arthritis, spondylosis can affect the spine’s facet joints—inflammation, stiffness, pain. It may develop in the neck (cervical spondylosis), mid back (thoracic spondylosis) and/or low back (lumbar spondylosis). Spondylosis is part of other degenerative changes too that cause spinal stenosis and disc herniation.
When one vertebral body moves forward over the vertebra beneath, the diagnosis is spondylolisthesis. While the disorder more commonly affects the lumbar spine, it can occur in the neck. The diagnosis includes the degree of the vertebral slip. Grade 1 mean the vertebra has slid forward by ~25% and Grade 5 is a complete slip (spondyloptosis). Grade 5 may be caused by fracture of the bone that helps stabilize the position of the vertebral body. Besides pain, that can be severe, muscle spasms, and sciatic-type symptoms may develop.