Scoliosis is an abnormal lateral curvature of the spine, where the vertebral column bends sideways into an “S” or “C” shape. While often associated with childhood or adolescence, it is also a significant health concern for adults. Adult scoliosis is common, particularly as the population ages and the spine experiences natural wear and tear. This spinal deformity can be a source of chronic pain and functional limitation for millions of adults worldwide.
Defining Adult Scoliosis and Its Types
A diagnosis of scoliosis requires a spinal curve measuring 10 degrees or more on an X-ray image. Adult scoliosis is separated into two categories based on its origin. The first type is Adult Idiopathic Scoliosis, which occurs when a curve that started in childhood or adolescence persists or progresses after skeletal maturity. The cause of this curvature remains unknown, which is what “idiopathic” means.
The second type is Degenerative Scoliosis, often referred to as “de novo” scoliosis (meaning “new”). This form develops later in life, typically after age 40 or 50, due to age-related changes in the spine. Degeneration of the intervertebral discs and facet joint arthritis causes the spine to become unstable and collapse sideways, most often in the lumbar (lower) spine. Understanding the type is important because the underlying cause, progression rate, and potential treatments differ significantly between the two classifications.
The Prevalence of Adult Scoliosis
The frequency of adult scoliosis is high, and prevalence estimates vary depending on the age group studied and the diagnostic criteria used. Studies focusing on the general adult population report prevalence rates ranging from 2.5% to 25% of individuals having some degree of curvature. The occurrence of scoliosis is strongly tied to age, with rates increasing substantially after the age of 50.
Prevalence estimates for degenerative scoliosis alone show that approximately 13.2% of adults under the age of 60 have the condition, rising to about 35.9% in those over 60 years old. Broader studies using the 10-degree curve threshold have found that between 32% and 68% of individuals aged 65 and older have scoliosis. The condition also shows a higher incidence in females, with some data showing a prevalence of 41.2% in women over 60 compared to 27.5% in men in the same age bracket. While mild curves are common, clinically significant curves—those exceeding 25 to 30 degrees—are less frequent but still represent a substantial number of older adults requiring monitoring.
Common Signs and Symptoms in Adults
Unlike the adolescent form, which is often painless, the primary symptom in adults with scoliosis is chronic pain, particularly in the lower back. This pain results from the uneven loading and stress placed upon the spinal joints and surrounding muscles due to the abnormal curvature. Muscle fatigue and stiffness often manifest after standing or walking for extended periods.
Neurological symptoms are also a common complaint, especially with degenerative scoliosis in the lumbar region. As the spinal canal narrows and the vertebrae shift, nerve roots can become compressed, leading to a condition called radiculopathy. This nerve irritation can cause shooting pain, tingling, numbness, or even weakness that radiates down into the legs. Physical signs, while sometimes subtle, can include a noticeable asymmetry, such as uneven shoulders or hips, or a slight shift in the body’s center of gravity.
Diagnosing and Monitoring the Curve
Diagnosis of adult scoliosis begins with a physical examination and is confirmed through medical imaging. The standard diagnostic tool is a full-length standing X-ray of the entire spine, which allows clinicians to visualize the curve under the influence of gravity. This accurately measures the degree of curvature and assesses the overall spinal alignment.
The severity of the curve is quantified using the Cobb angle, which is calculated by drawing lines on the X-ray along the top and bottom of the most-tilted vertebrae within the curve. Monitoring the progression of the Cobb angle over time is important, especially for curves that measure over 30 degrees, as these are at a higher risk of worsening. Other imaging modalities, such as CT scans or MRIs, may be used to evaluate for nerve compression or to rule out other causes of back pain, such as tumors or fractures.