The Causes of Low-Back Pain
Ah, the concrete jungle of NYC. The food, the nightlife, the millions of people slouched over their desks all day and putting excessive strain on their intervertebral discs! There's nothing quite like it.
Welcome back to the Strong Healthy Happy blog for part 2 of our 4 part series on low-back pain (LBP). In part 1 we got our asses kicked by LBP. Now dial up your favorite cliché halftime speech (here's a classic from the great James Van Der Beek. Come on JVDB, when are you going to drop Varsity Blues 2 on us!?) and let's figure out what we are going to do about it!
We have reviewed the scientific literature on the causes of LBP and summarized it for you here. Once we understand what causes LBP, we can figure out how to prevent it. Here is what you need to know. Enjoy.
We are focusing on the lowest articulating region of the spine, i.e., the lumbar region, which consists of five vertebrae separated by intervertebral discs and is surrounded by a number of ligaments, muscles, tendons, blood vessels and nerves (3,8).
The bony parts of the spine. The spinal cord and nerve roots pass through the spinal canal behind the vertebral body. Vertebrae articulate with adjacent vertebrae through the facet joints (3,8).
Separates adjacent vertebrae and acts as a shock absorber for the spine. It consists of two components, a gelatinous center called the nucleus pulposus and a tough outer layer called the annulus fibrosus (3,8). Think of it like a jelly donut.
Nervous tissue that runs through the spinal canal and connects the body with the brain. Nerves branch off of the spinal cord and travel to all different parts of the body. Five nerve roots branch off in the lumbar region and travel down into your butt, legs, and feet (3,8).
The definitions tend to be a bit variable, but generally acute pain is brought on by a specific event or injury and subsides when the injury heals (typically within 12 weeks)(9). Sprains of ligaments and strains of muscles and tendons are common examples of injuries which cause acute musculoskeletal pain in the low-back (7).
Again, the timeframe can be a bit variable, but generally chronic pain persists beyond 12 weeks and can be difficult to treat because it’s not linked to a specific injury (1). Chronic pain may be caused by degenerative changes associated with aging, muscular deficiencies and imbalances, poor posture, nerve damage, and in some cases is unknown.
The pain can be musculoskeletal or neurologic in origin, and often times the two are intertwined. Neurologic pain in the lumbar spine arises when a nerve is compressed by a displaced vertebrae or herniated disc, and can cause pain, numbness, tingling, and weakness to radiate to other parts of the body where the nerve travels, often times the butt, legs, and feet (radiculopathy)(6,8). Compression of the sciatic nerve can lead to symptoms commonly described as ‘sciatica.’
Musculoskeletal pain arises from bones, muscles, tendons, ligaments, intervertebral discs, and articulating facet surfaces. Arthritis at the facet joints is an example chronic pain and can be brought on by degenerative changes to the spine (7). Degenerative changes to the musculoskeletal system can lead to neurologic pain as well. Degenerative disc changes are often what lead to nerve compression, with disc herniations, spondylolisthesis, and spinal stenosis commonly associated with declining disc tissue quality (8).
Bulging & Herniated Disc
Degenerative changes of the disc are a normal part of aging, and as the disc begins to compress more and lose height, it naturally ‘bulges’ out. Disc herniation occurs when the annulus of the disc ruptures and the nucleus herniates through the outer wall, which can then lead to painful conditions such as compression of the spinal nerves (6,10).
Facet Joint Osteoarthritis
Natural degeneration of the disc as people age can result in the loss of disc height, forcing the facets to carry more weight and breakdown of the articular cartilage (4,8). Similar to arthritis at other joints, such as the knee and hip, this can lead to pain and stiffness.
The narrowing of the spinal canal, which can lead to compression of the nerve roots and associated symptoms (2,8). Narrowing is a result of a cascade of degenerative changes. When the facet joints become arthritic, as described above, they may develop osteophytes (bone spurs) that impinge on the nerve roots. Similarly, degenerative changes may cause a vertebrae to slide out of position and narrow the spinal canal (spondylolisthesis).
Another condition that results from a cascade of degenerative changes as we age. The declining health of the disc, ligaments, and facet joints allows a vertebrae to slip out of alignment and can cause stenosis and painful compression of the nerves (5).
You may be sensing a common theme here. Chronic LBP is often associated with normal degenerative changes of the spine as we age. This may be bit a frightening for you because it suggests LBP is ‘normal’ and there is nothing we can do about it. However, it’s important to keep in mind that as our discs, ligaments, and joints age, there is plenty of work we can do to support the healthy alignment and function of our spine so that those structures don’t have to do all the work. In fact, it’s not uncommon (30%) for individuals to have signs of disc degeneration without any pain (6). Working on core strength, mobility, and posture can help prevent LBP, even as those structures start to show the signs of aging. More on this next week.
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