The Cobb angle is an X-ray measurement of the spine that doctors use to diagnose scoliosis, monitor spinal curvature, and determine treatment options.
Scoliosis is an abnormal sideways curvature and twisting of your bony spinal column. Scoliosis is quite common. Its most prevalent form, called adolescent idiopathic scoliosis (AIS), occurs in approximately
Doctors frequently use spine X-rays to diagnose scoliosis, monitor curve progression, and check response to treatment. For these purposes, doctors usually refer to a specific measurement on your scoliosis X-rays called the Cobb angle.
Beginning in the
Keep reading to learn more about the Cobb angle and how healthcare professionals use it for scoliosis.
Your bony spinal column comprises 33 stacked bones called your vertebrae. Physicians determine the Cobb angle using a standing front-to-back X-ray of your whole spinal column.
In the curved region of scoliosis, doctors look at the first and last abnormally tilted vertebrae. These are called the terminal vertebrae. Then, they draw a horizontal line along the top of the upper terminal vertebra and the bottom of the lower terminal vertebra. The angle where these two lines intersect is called the Cobb angle.
Most digital radiology viewing programs now have software that assists with calculating this angle. When using these programs, Cobb angle measurements are very accurate, with a typical error range of just
Doctors use the Cobb angle to diagnose scoliosis and to monitor progress and treatment.
Diagnosing scoliosis
Scoliosis screening exams
If there is concern for significant scoliosis, you will typically be referred for spine X-rays.
Healthcare professionals can confirm a diagnosis of scoliosis when X-rays show a lateral spinal curve and rotational deformity with a Cobb angle measuring at least
Monitoring the progression of spinal curvature
Although scoliosis may occur at any age, it is most often identified in the preteen and early teen years.
During the pubertal growth spurt, spinal curvature in scoliosis can rapidly worsen. If your child has scoliosis, your doctor will most likely monitor their curve closely until the point of skeletal maturity, when most height growth is complete.
Monitoring will include regular physical exams and X-rays comparing Cobb angle measurements every 6 to 12 months.
If your child begins conservative scoliosis treatments such as physiotherapy or bracing, your doctors will also need repeat X-rays and Cobb angle measurements to monitor for improvement or progression.
Determining treatment options
The Cobb angle can also help predict the outlook for a person with scoliosis and guide treatment decisions. Treatment options depend on your age, skeletal maturity, and specific spine deformity.
The goals of treating scoliosis include:
- stopping or reversing curve progression in puberty
- preventing lung problems and back pain
- improving aesthetics with posture correction
Doctors know that when Cobb angles
But many people with milder idiopathic scoliosis will not progress and do not require treatment. For example, mild scoliosis of 10 to 20 degrees is often managed simply with close observation.
Wearing a scoliosis brace may be recommended for idiopathic scoliosis in children (whose skeletons are still growing) at Cobb angles of 25 to 40 degrees. Sometimes, bracing is recommended at lesser Cobb angles, especially when scoliosis is rapidly progressing or your child has a lot of growing left to do.
For Cobb angles of
What Cobb angle requires surgery?
According to the American Association of Neurological Surgeons (AANS), surgery in children may be considered for scoliosis curves with Cobb angles over 40 degrees with signs of progression.
In adults with scoliosis, surgery may be recommended when the Cobb angle is greater than 50 degrees, and the patient has pain or other neurological symptoms.
What Cobb angle requires a brace?
Bracing is generally considered in growing children with scoliosis Cobb angles of
Bracing of lesser curves may be indicated when they are progressing rapidly (
Is the Cobb angle used for other spinal conditions?
The Cobb angle is mainly used in the diagnosis and management of scoliosis, defined as an abnormal sideways curvature and twisting of the spine.
But using X-rays taken in other orientations, healthcare professionals may also use the Cobb angle to quantify other types of abnormal spinal curvatures, such as kyphosis and lordosis.
The Cobb angle can also be helpful in the surgical treatment of certain types of spinal fractures.
Scoliosis is a common spinal disorder that involves abnormal sideways curvature and twisting of the vertebral column.
Many people without scoliosis have a slight sideways spinal curvature. However, doctors diagnose scoliosis when a specific X-ray measurement, called the Cobb angle, reaches 10 degrees or greater.
The Cobb angle is useful in diagnosing scoliosis. But doctors can also use serial Cobb angle measurements when:
- tracking scoliosis progression
- determining treatment options
- evaluating your response to therapy
If you or your child has scoliosis, talk with your doctor about your Cobb angle measurements and what they mean for you.