Mild Scoliosis: What it is and what to do about it

Written and reviewed for scientific and factual accuracy by Dr. Austin Jelcick, PhD and Dr. Matthew Janzen, DC. Last reviewed/edited on March 10, 2020.

Mild scoliosis commonly refers to any idiopathic scoliosis curve that is less than 20 degrees. Traditionally, kids and teens with mild scoliosis were told to “watch and wait”, having x-rays taken every 6 or 12 months to keep an eye on the curve and make sure it isn’t getting worse. However, we know from current scientific research that “watch and wait” is not an acceptable course of action as curves can rapidly worsen when a child hits their growth spurt. So what should someone with a mild scoliosis do? Are there any symptoms or indications that a mild scoliosis might worsen into a moderate or severe curve? What is the probability that a mild scoliosis will worsen to the point that it requires surgery?

The good news is that the best time to treat a scoliosis is when it is mild: when the curve is small and the child is young and skeletally immature

Research shows that early detection and early intervention when curves are small provides better treatment outcomes 1-3, so let’s learn why and also see what warning signs we can look out for so idiopathic scoliosis never sneaks up on us.

Mild scoliosis: How easy is it to detect?

Detecting a mild scoliosis can be a challenging task for several reasons. You might think that when a curve is present in the spine that a child or teen might have some pain but this isn’t the case. In fact, it is quite rare for kids to feel pain when they have scoliosis even when the curve is quite large 4. Because the scoliosis is idiopathic, there aren’t typically any other health problems. In contrast, when scoliosis is neuro-muscular or congenital there are often other problems such as in neuro-muscular patients who often are unable to walk around on their own 5.

Because of the lack of symptoms, efforts have been made to try and catch mild scoliosis cases early through pro-active school screenings. However even this has proven difficult due to problems with the screening process. Sadly, these problems and the inaccuracy of traditional school screenings have resulted in several states in the US ending their school screening programs.

Any good screening method should have excellent sensitivity and excellent specificity. Sensitivity measures how well positive cases (kids who actually HAVE scoliosis) are detected, while specificity measures how well negative cases (kids who DON’T have scoliosis) are detected. The “gold standard” for scoliosis screening across the world has traditionally been one or more of the four following tests 6:

  • Adam’s forward bending test
  • Measuring rotation with a scoliometer
  • Measuring any rib hump that is present
  • Using moiré topography to make a 3D image of the back

Now you might wonder why all these different tests are used for screening when you could simply take an x-ray of the spine and know instantly if a curve is there. The problem with taking x-rays for screening is the same reason why so many doctors traditionally used “watch and wait” even when kids were getting worse: radiation.

The problem of x-ray in screening

The concept of “watch and wait” and only checking the spine with x-ray every 6 to 12 months isn’t because we only need to look once or twice a year but rather it is an attempt to limit radiation from the x-ray. Studies have shown increased risks of cancer for those with scoliosis due to all of the x-rays they are exposed to over their lifetime 7. Thus, in an effort to limit radiation exposure, doctors only look every 6 to 12 months. This same idea of avoiding radiation exposure from x-ray is why it isn’t used for scoliosis screenings, and is also one reason school screenings have been stopped in some states (more on this later).

Because x-ray is essentially condemned due to the potential harm to the child (and the cost 6), screening for and detecting a mild scoliosis has to rely on other methods like the four we mentioned earlier. Unfortunately, these methods vary in their accuracy and frequently result in a high number of false positives. While a false positive doesn’t seem like a big deal, when you understand that a positive screen means the child is referred to their doctor for an x-ray to confirm the findings, the problem becomes a big deal. Once again we are giving kids x-rays who don’t need them; exposing them to harmful ionizing radiation when it isn’t necessary. A false negative is bad as well as a kid with scoliosis now goes unnoticed, and their curve is allowed to worsen unchecked.

If screening for a mild scoliosis curve doesn’t allow x-ray and the standard methods of screening result in false positives, it’s no wonder that schools gradually stopped performing screenings. School screenings cost money, and a large number of kids were being sent off for x-rays when they didn’t have scoliosis 8. Thus, school districts and states found it easy to cut screening out of the budget such as with California which hasn’t had school scoliosis screenings since 2010.

What is the chance that a mild scoliosis becomes severe or requires surgery?

One of the biggest problems with scoliosis is that it can get rapidly worse when a child goes through their growth spurt during puberty: the adolescent growth spurt. The problem here is that if a child has a mild scoliosis when they are young, but it won’t get drastically worse until they hit their adolescent growth spurt, how can we know whether or not we should take action? If science shows treatment is more successful when curves are small and the child is young, how can we know we need to act now?

Thankfully, recent research has come up with mathematical equations that we can use to predict whether a curve will get worse (progress) and whether or not it will progress to the point that it needs surgery. To quickly summarize, these equations (sometimes called prognostic models) are developed by looking at patients with untreated idiopathic scoliosis and looking to see what variables influence whether or not their curves progress, and whether or not they progress to surgical range (40-50 degrees). While not perfect, these models provide a strong, science based probability that a curve will worsen.

What is the chance that a small curve will progress?

The first question most people have before they worry about surgery is simply wondering whether or not their curve or their child’s curve will get worse. When a curve gets worse it is commonly known as “progressing”. Thus determining the probability of curve progression is important because it lets us know how likely it is that the scoliosis curve will get worse.

When we look at the scientific model for curve progression, it is first important to define what we mean by progression: if the curve gets worse, how much worse will it get? The criteria that is used is based on the initial size of the curve. For curves 19 degrees or less, progression is defined as an increase of at least 10 degrees where the curve is bigger than 20 degrees at the end. Similarly for curves 20-29 degrees (or larger) progression is defined as an increase of at least 5 degrees or more 9.

Curve progression is defined as an increase of 10º or more for curves 19º or less, or an increase of 5º or more for curves 20-29º

Using these criteria we can approximate the likelihood that a mild scoliosis curve will progress, keeping in mind that to be “mild” our curve needs to be less than 20 degrees to begin with. It is also important to remember that for a curve to even be diagnosed as scoliosis, it needs to be larger than 10 degrees. Last but not least while a child’s age can be important, their bone age (skeletal maturity) is even more important because it lets us know approximately how much growth they have left (scoliosis gets worse as a child hits their growth spurts). So what do our chances of progression look like?

Age Risser Curve Size Probability of Progression

If you look at these estimates, you can see that if a child’s skeletal maturity stays the same, as they get older their risk of progression decreases. However we can also see that a mild scoliosis can have almost a 100% chance of getting worse when it is detected in a very young, skeletally immature child. If we look at kids who are just beginning their adolescent growth spurt the numbers change once again.

Age Risser Curve Size Probability of Progression

As you can see, the older and more skeletally mature the child is when diagnosed with a mild scoliosis, the lower the risk that their curve will progress. Again, this is because scoliosis worsens rapidly when the body is going through periods of rapid growth. Therefore as the child becomes older and more skeletally mature, they have less growing left to do and as they progress through puberty how fast they grow begins to slow down. On the other hand it is also easy to see why a child who is diagnosed at a young age has such a high likelihood of worsening. Thus the younger the child is when mild scoliosis is diagnosed, the bigger the risk the curve will get worse.

What is the chance that a small curve will need surgery?

While calculating the probability that a curve will worsen is important, it doesn’t answer the question that is on every parents’ mind when they first learn their child has scoliosis: will the curve need surgery? To determine the chance that a mild scoliosis will worsen to the point that surgery is needed (40-50 degrees) we need a new equation 10.

While our progression calculator is based on the size of the curve, how old the child is, and how skeletally mature they are, to calculate the probability of surgery we need to know something else: the location of the curve. The likelihood that a curve will require surgery drastically increases when the curve is located in the thoracic area of the spine. If a curve is located in the lumbar or thoracolumbar region the chances of surgery decrease. It’s also interesting to know that we only need to know how skeletally mature the child is and not how old they actually are; this is simply because the child’s age wasn’t found to be significantly associated with the risk of surgery.

Let’s look at some examples and see how our risk of surgery changes depending on the size and location of the curve, as well as the skeletal age of the child. Keep in mind that Risser and Sander’s score/scale are simply two different methods of determining skeletal maturity: the lower the number, the less mature the child is. It is also useful to know that a young girl who is a 2 on the Sanders scale (2 out of 8) has JUST STARTED her adolescent growth spurt but has not yet reached her fastest rate of growth during puberty.

The Risser and Sander’s scale are two different ways to determine skeletal maturity

Sanders Score Curve Size Curve Location Probability of Surgery
1-211Any thoracic curve13.26%
1-215Any thoracic curve28.91%
1-219Any thoracic curve51.96%

What we see is that for a skeletally immature child who has a lot of growing left to do, being diagnosed with mild scoliosis in the lumbar/thoracolumbar region can mean anywhere from a 3% to a 20% chance that the curve will worsen to the point where it needs surgery. But if the curve is located in the thoracic, our chances for surgery skyrocket with an over 50% chance of surgery when the curve is only 19 degrees at diagnosis.

Again, this is for young skeletally immature kids. This again makes sense because if the curve is already 19 degrees BEFORE they have hit their growth spurt, you can imagine how it can rapidly worsen once that growth spurt hits. Just as before when we calculated the chance of progression, as a child matures their risk of surgery decreases.

Sanders Score Curve Size Curve Location Probability of Surgery
319Any thoracic curve9.78%
4+19Any thoracic curve1.39%

Looking for other warning signs

We know that major risk factors for a curve getting worse or needing surgery are:

  1. The size of the curve
  2. How skeletally mature the child is
  3. The location of the curve

However we also know that standard screening methods can be error prone, and it can be difficult to detect a mild scoliosis without using x-ray which has its own risks. Are there other warning signs or symptoms to keep an eye out for that would suggest a child has scoliosis?

We’ve talked before about the rib hump that is a hallmark feature of scoliosis and how it develops as a way to relieve tension on the tight spinal cord and nerves. As the body tries to provide the cord with the shortest path possible as the patient bends over (Adam’s forward bending test), the spine rotates resulting in the classic rib hump. However it is also possible that the back will simply be flat as the body tries to relieve tension and the patient won’t be able to bend over normally and touch the floor. Thus a noticeable lack of flexibility or a flat back when bending can be an early warning sign of scoliosis.

Another early warning sign can be found when looking at the hands and the feet. Having flat feet or being hyper-mobile is a sign that the ligaments are not as tight compared to your average individual. Ligament laxity (loose ligaments) or joint hyper-mobility can be an early warning sign of scoliosis because it means that the ligaments are more susceptible to any forces which might pull on them. In the case of idiopathic scoliosis where the nerves are tight, this increased nerve tension provides an extra “pulling” force that the ligaments may not be able to handle, resulting in a higher risk of scoliosis developing. In fact, in diseases like Marfan’s Syndrome 11 and Ehler’s Danlos Syndrome 12 where the soft connective tissues (ie. ligaments) are affected and loose we see scoliosis occurring quite often.

When should mild idiopathic scoliosis be treated?

If we know that even a mild scoliosis can get worse and sometimes need surgery, when is the best time to treat it? As we discussed earlier one of the biggest factors is how skeletally mature the child is. The less mature the child is when the curve is detected, the higher the risk and thus the more urgent it is to begin treating it to “stay ahead of the curve.” We know from current scientific research that when detection and intervention are done early, surgery can be prevented 13 and curves can be reduced long-term 15. However early treatment doesn’t always mean bracing as physiotherapeutic exercises (PSSE) can often help 14. Bracing can always be used later if necessary, and we know from science that bracing is effective at reducing curves and preventing surgery as well 2.

The biggest take home message here is simply that the earlier the scoliosis is caught and treated, the better the outcome. While using x-ray to monitor a mild scoliosis isn’t wise because of the radiation exposure, monitoring with alternative methods such as a weight bearing (standing) MRI can be easily done so that any changes to the curve are caught quickly. Treating early not only helps prevent any structural changes or contractures from forming, but also allows us to utilize that worrisome adolescent growth spurt to our advantage as a corrective force 3.

With early detection and early intervention idiopathic begins to look like any other treatable condition

Another important take home message that we can learn from our progression and surgical calculators is that treatment needs to be continued until skeletal maturity is reached. The more skeletally mature the child is, the lower the risk of progression and surgery. Thus if we treat a scoliosis and keep the curve small until the body has stopped growing, we can rest assured that our results will last a long time 15.

When we take the time to understand scoliosis; what can cause it; what influences it getting worse; when it tends to get rapidly worse; and when the risk for worsening is minimized; we can come up with a winning game plan for treatment. Combined with novel methods for early detection (ie. using standing MRI and looking for early warning signs), mild idiopathic scoliosis begins to look less like a boogeyman and more like any other treatable condition.


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