Scoliosis is defined as an abnormal side-to-side curvature and twisting of the spine, often presenting in an S or C shape. Severity is measured using the Cobb angle, determined from a spinal X-ray. A diagnosis is confirmed when the Cobb angle measures 10 degrees or greater. Scoliosis can worsen with age, but the reasons and rate of progression shift dramatically once the spine has finished growing.
Progression During Growth
Progression of a scoliotic curve is most strongly correlated with the remaining growth potential of the individual, particularly during the adolescent years. Adolescent Idiopathic Scoliosis (AIS) is the most common form, typically appearing around the age of 10 or later. The largest risk for curve worsening occurs during the pubertal growth spurt, a period of rapid spinal lengthening.
During this time, a mild curve can quickly accelerate, sometimes necessitating immediate intervention. Professionals assess skeletal maturity using methods like the Risser sign, which tracks bone formation on the pelvis to estimate remaining growth. The younger a patient is, the higher the risk that the curve will progress significantly. For instance, a curve measuring 30 degrees at the onset of puberty may have a nearly 100% chance of progressing further if not treated.
Progression After Skeletal Maturity
Once an individual reaches skeletal maturity, typically in the late teens, the mechanism driving curve progression changes entirely. The spine is no longer lengthening rapidly, removing the main catalyst for worsening curves. However, progression does not halt completely, especially if the curve was already substantial.
Progression in adulthood is primarily driven by mechanical instability and age-related degenerative changes. Intervertebral discs begin to thin and lose height, and arthritis can develop in the facet joints, leading to a loss of spinal stability. This asymmetrical deterioration can cause the spine to shift further out of alignment, a condition called adult degenerative scoliosis. For those with pre-existing adolescent curves, the curvature creates an uneven load, accelerating this wear-and-tear process.
Key Factors That Predict Worsening
The most important factor determining future progression is the Cobb angle magnitude at skeletal maturity. Curves measuring less than 30 degrees have a very low likelihood of progressing significantly throughout adult life, often remaining minimal or non-existent.
In contrast, curves measuring 50 degrees or more at skeletal maturity are highly likely to progress over time, typically at a rate of about 1 to 2 degrees per year. The curve acts as a mechanical lever arm, continuously pulling the spine out of alignment due to asymmetrical loading. Curve location also serves as a predictor; double curves and those involving the lumbar spine often have a higher risk of worsening and causing greater symptoms in adulthood.
Monitoring and Management of Progression
Monitoring scoliosis progression involves regular clinical assessments and periodic X-rays to accurately track the Cobb angle. A change of 5 degrees or more over time is generally considered a significant progression requiring a re-evaluation of the treatment plan. For adolescents who are still growing, bracing is often recommended for moderate curves, usually between 25 and 40 degrees, to prevent further worsening during growth spurts.
Bracing is typically worn for many hours a day and is discontinued once skeletal maturity is reached. Physical therapy and specialized exercises are a standard part of management for both adolescents and adults. These programs focus on core strengthening and improving postural control to manage symptoms and potentially slow progression. In adults, managing the underlying degenerative changes and related pain is a primary focus of conservative treatment.