Adult scoliosis has two main causes: spinal degeneration that develops new curvature later in life, and childhood scoliosis that was never diagnosed or that worsens over time. The condition is far more common than most people realize. One study of healthy volunteers with an average age of 70.5 found that 68% met the clinical definition of scoliosis, a spinal curve greater than 10 degrees. Understanding which type you have matters because the underlying mechanism, the symptoms, and the outlook differ significantly.
Degenerative Scoliosis: The Most Common Cause
The most frequent cause of new spinal curvature in adults is age-related wear and tear, sometimes called de novo degenerative scoliosis. It starts when the discs between your vertebrae and the small facet joints that connect them begin to break down unevenly. If the left side of a disc wears faster than the right, the vertebra above it tilts slightly. Multiply that across several spinal segments and the result is a visible curve that wasn’t there before.
This process is self-reinforcing. Once a slight asymmetry develops, it shifts the load on your spine so that the already-worn side bears even more pressure, which accelerates the degeneration further. Researchers have identified six key factors that drive this cycle: uneven disc and joint wear, inflammation and abnormal blood vessel growth within the discs, breakdown of the structural tissue inside the disc, changes in bone metabolism, age-related muscle loss (sarcopenia), and irregular distribution of mechanical stress along the spine. Together, these create a feedback loop where the curve gradually worsens.
This type of scoliosis typically appears after age 40 and becomes increasingly common with each decade. It develops most often in the lumbar (lower) spine, where the load-bearing demands are greatest.
Undiagnosed Childhood Scoliosis That Progresses
Many adults with scoliosis actually had mild curves during adolescence that were never caught. A slight curve of 15 or 20 degrees in a teenager can go completely unnoticed, causing no pain and no visible asymmetry. Decades later, as the spine ages and loses structural support, that once-stable curve begins to progress and produce symptoms for the first time.
Research tracking adults whose adolescent curves measured 40 to 50 degrees found that those with progressing curves worsened by an average of about 1.5 degrees per year. Fast progressors lost about 3 degrees per year. That may sound small, but over 10 or 20 years it adds up to a meaningful change in spinal alignment and can cross the threshold into pain, stiffness, or visible postural shift. Curves above 50 degrees are the most likely to keep progressing in adulthood.
How Osteoporosis Creates New Curves
Osteoporosis is a major contributor to adult scoliosis, particularly in postmenopausal women. When bone density drops low enough, vertebrae can fracture under forces as minor as bending forward or even coughing. These vertebral compression fractures are the most common type of osteoporotic fracture, and they typically crush the front of the vertebral body more than the back, producing a wedge-shaped deformity.
A single wedge fracture tilts the spine forward. Multiple fractures across several vertebrae can create a pronounced curve or worsen one that already exists. The altered alignment then places extra stress on the vertebrae above and below the fracture, raising the risk of additional fractures in a cascading pattern. Left untreated, this sequence can progress to significant spinal deformity, chronic pain, and serious limitations in daily activities.
Neuromuscular and Secondary Causes
Conditions that affect the muscles or nerves supporting the spine can also produce scoliosis in adulthood. Spinal cord injuries, particularly those occurring during childhood or adolescence, frequently lead to progressive neuromuscular scoliosis as the muscles on one side of the spine weaken or become paralyzed. Conditions like muscular dystrophy, cerebral palsy, and Parkinson’s disease can have similar effects, creating muscle imbalances that pull the spine out of alignment over time.
Previous spinal surgery is another recognized cause. Procedures like laminectomy, which removes part of the vertebral bone to relieve nerve pressure, can sometimes destabilize the spine by removing the bone and soft tissue that kept it aligned. This is known as iatrogenic instability. It has been documented throughout the spine: cervical kyphosis after neck laminectomies, thoracic instability after certain joint resections, and degeneration of the segments adjacent to a spinal fusion. Not everyone who has spinal surgery develops this problem, but it is a known risk, particularly after multilevel procedures.
Why Adult Scoliosis Causes Pain
Scoliosis in children is often painless, which is one reason it goes undetected. In adults, the picture is different. The same degenerative changes that create the curve also narrow the spaces where spinal nerves exit, a condition called spinal stenosis. The pattern of nerve compression is specific and predictable. In one study of patients with degenerative lumbar scoliosis, the L4 nerve root was affected in 68% of cases and the L5 root in 55%.
Where the nerve gets pinched depends on which side of the curve you’re looking at. On the concave (inner) side, the vertebrae compress together, squeezing the nerve roots higher up in the spine through the narrowed openings where they exit. On the convex (outer) side, the stretching and sliding of vertebrae tends to compress nerve roots lower in the spine through a different mechanism. This means that leg pain, numbness, or weakness from scoliosis-related nerve compression can show up on either side, and the location of your symptoms gives your doctor useful information about where the problem originates.
Beyond nerve compression, the postural imbalance itself is a source of pain. When the spine curves, the muscles on one side work harder to keep you upright, leading to chronic fatigue and spasm. The facet joints on the compressed side bear abnormal loads, accelerating arthritis in those joints. And if the spine’s overall balance shifts so that your head or trunk no longer lines up over your pelvis, the constant muscular effort to compensate can produce widespread back pain and difficulty standing for long periods.
Risk Factors That Speed Progression
Not every adult with a spinal curve will see it worsen. Several factors influence whether a curve stays stable or progresses. The size of the existing curve is the strongest predictor: curves above 30 degrees are substantially more likely to progress than smaller ones. Low bone density accelerates the process by weakening the vertebrae that resist the curve. Loss of muscle mass, which happens naturally with aging but is worsened by inactivity, removes another layer of spinal support.
Disc degeneration is both a cause and an accelerator. As discs lose height, the vertebrae settle unevenly, and the facet joints are forced into positions they weren’t designed for. Smoking, which impairs blood flow to spinal tissues and accelerates disc breakdown, is a modifiable risk factor. Carrying excess body weight increases the compressive load on an already-compromised spine. Taken together, these factors explain why degenerative scoliosis tends to worsen in later decades, when bone loss, muscle loss, and cumulative disc wear converge.