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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Adolescent Idiopathic Scoliosis

Assessing Growth and Progression Risk

At a Glance

In adolescent idiopathic scoliosis, curve progression is most likely when a moderate or large curve is present during rapid growth. Doctors combine the Cobb angle, curve location, Risser or Sanders maturity score, and triradiate cartilage status to estimate risk and plan monitoring.

Understanding the risk of your curve getting larger is the most important part of your diagnosis. In Adolescent Idiopathic Scoliosis (AIS), the spine doesn’t just curve at a random speed; it tends to “accelerate” during periods of rapid growth [1][2].

Because of this, your doctor is less interested in your birthday and more interested in your skeletal age—how much your bones have grown and how much growing they have left to do [3]. This page explains the tools doctors use to estimate the future of your curve.

Why Growth Matters

The biggest risk factor for a curve progressing (getting worse) is having a significant amount of growth remaining while already having a moderate curve [4].

  • Peak Height Velocity (PHV): This is the medical term for your “growth spurt”—the time when you are growing the fastest.
  • The Curve Lag: Interestingly, curve progression usually peaks about 7 months after your fastest height growth [2]. This means even after you seem to stop getting taller, your spine may still be at risk for another year or more [5].

How Doctors Measure Maturity

To see where you are in your growth journey, doctors look at specific “growth plates” on your X-rays. It is important to know that these markers—along with height velocity and menarche—are complementary, imperfect clues rather than exact timers.

1. The Risser Sign (0 to 5)

The Risser sign is a 0-to-5 scale based on the growth of the hip bone (the iliac apophysis) [6].

  • Risser 0: No growth visible on the hip bone yet; this indicates the most growth remaining and generally a higher risk for progression, though it covers a broad span of time [7].
  • Risser 1–3: You are in the middle of your growth spurt.
  • Risser 4–5: Growth is slowing down or has finished; the risk of the curve getting significantly worse drops as you reach these stages [7][8].

2. The Sanders Score (1 to 8)

Because the Risser sign can be a bit “coarse,” many specialists now use the Sanders Maturity Scale, which uses an X-ray of the hand [3]. It is much more precise:

  • Sanders 2: This stage occurs about 9 months before your peak growth spurt. If you have a curve over 25 degrees at this stage, the risk of it getting worse is very high [9][10].
  • Sanders 3: This is the higher-growth period where you are right in the middle of your peak growth [6].
  • Sanders 7–8: This indicates you have reached the “growth plateau” where spinal growth is nearly finished [6][11].

3. Triradiate Cartilage (TRC)

Your doctor will also look at the triradiate cartilage, a Y-shaped growth plate in the hip socket.

  • Open TRC: This is an early warning sign that you are very immature and have generally not yet reached your peak growth spurt. It suggests the curve could progress rapidly [12].
  • Closed TRC: This typically happens as you enter the peak of your growth spurt [12].

Predicting the Risk

Doctors combine your Cobb angle (the size of the curve), your curve pattern, and your maturity score to estimate risk. These are population estimates, not guarantees for your individual spine.

Maturity Level Cobb Angle Progression Risk
High Growth (Sanders 2-3, Risser 0-1) > 25° Very High: High risk in some cohorts; very close monitoring or treatment discussion is common [10].
High Growth (Sanders 2-3, Risser 0-1) 10°–20° Moderate: Requires very close monitoring [13].
Near Mature (Sanders 7, Risser 4) < 30° Very Low: Progression is unlikely once growth stops [10].
Near Mature (Sanders 7, Risser 4) > 40° Moderate: Large curves can still progress slowly even after growth [11][8].

Curve Pattern and Location

The location of the curve also matters. Thoracic curves (located in the middle back) generally have a higher risk of getting worse than lumbar curves (located in the lower back) [14][15]. If you have a thoracic curve over 25 degrees and you are still Risser 0, your care team will likely discuss starting treatment like bracing as a common point of intervention to help manage the curve during your highest growth period [16][17].

Ultimately, the goal of measuring maturity is to determine how “aggressive” the monitoring or treatment needs to be during the relatively short window of time when your spine is growing the most.

Common questions in this guide

Why does having growth remaining increase the chance that scoliosis will worsen?
A curve is more likely to progress when a moderate or large curve is present while the spine is still growing quickly. Risk often peaks after the fastest height growth, so it can remain important even when a teen has recently stopped getting taller. Doctors use growth markers to decide how closely to monitor the curve.
What is a Risser score, and how does it relate to scoliosis risk?
The Risser sign is a 0-to-5 rating based on growth of an area on the hip bone seen on X-ray. Risser 0 generally means more growth remains, while Risser 4 or 5 suggests growth is slowing or finished and the chance of major progression is lower. It is a helpful but imperfect estimate.
What does my Sanders maturity score mean?
The Sanders scale uses a hand X-ray to rate skeletal maturity from 1 to 8. Sanders 2 is usually before the fastest growth period, Sanders 3 is around peak growth, and Sanders 7 or 8 indicates that growth is nearly complete. This scale can provide a more precise estimate of growth remaining than the Risser sign.
Why does an open triradiate cartilage matter?
The triradiate cartilage is a Y-shaped growth plate in the hip socket. When it is open, it usually indicates early skeletal immaturity and that peak growth may not have occurred, so a scoliosis curve may have more opportunity to progress. When it closes, the patient is typically entering the peak growth period; it is one clue rather than an exact timer.
How are Cobb angle and curve location used to estimate progression risk?
Doctors combine the Cobb angle, the location and pattern of the curve, and skeletal maturity rather than relying on one measurement. Thoracic curves generally have a higher progression risk than lumbar curves, especially when the curve is over 25 degrees and the patient is still very immature. These are population-based estimates, not guarantees for one person's spine.
Can an idiopathic scoliosis curve worsen after growth is finished?
Progression becomes much less likely for a curve under 30 degrees once growth has ended. Larger curves, especially those over 40 degrees, can still progress slowly after skeletal maturity. Your clinician can use your current curve and maturity stage to plan follow-up.
When might bracing be discussed for adolescent idiopathic scoliosis?
Bracing may be discussed when a patient is still growing and has a curve at higher risk of progression, such as a thoracic curve over 25 degrees with very low skeletal maturity. It is not appropriate for every curve, so the decision depends on the Cobb angle, curve pattern, growth stage, and clinical assessment.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What are my specific Risser and Sanders scores, and what do they tell you about how much growth I have left?
  2. 2.Is my triradiate cartilage still open, and how does that affect the urgency of our next steps?
  3. 3.Based on my current Cobb angle and maturity stage, what is the statistical likelihood that my curve will reach 45 or 50 degrees?
  4. 4.When do you expect me to reach peak height velocity, and how will we monitor my curve during that high-risk window?
  5. 5.If my curve is already over 30 degrees but I am still very immature (like Sanders 2), should we be considering more aggressive treatment now?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (17)
  1. 1

    Scoliosis and Prognosis-a systematic review regarding patient-specific and radiological predictive factors for curve progression.

    Lenz M, Oikonomidis S, Harland A, et al.

    European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 2021; (30(7)):1813-1822 doi:10.1007/s00586-021-06817-0.

    PMID: 33772381
  2. 2

    Curve Progression in Adolescent Idiopathic Scoliosis Does Not Match Skeletal Growth.

    Cheung JPY, Cheung PWH, Samartzis D, Luk KD

    Clinical orthopaedics and related research 2018; (476(2)):429-436 doi:10.1007/s11999.0000000000000027.

    PMID: 29389797
  3. 3

    High Risk of Mismatch Between Sanders and Risser Staging in Adolescent Idiopathic Scoliosis: Are We Guiding Treatment Using the Wrong Classification?

    Minkara A, Bainton N, Tanaka M, et al.

    Journal of pediatric orthopedics 2020; (40(2)):60-64 doi:10.1097/BPO.0000000000001135.

    PMID: 31923164
  4. 4

    Bracing in Adolescent Idiopathic Scoliosis Trial (BrAIST): Development and Validation of a Prognostic Model in Untreated Adolescent Idiopathic Scoliosis Using the Simplified Skeletal Maturity System.

    Dolan LA, Weinstein SL, Abel MF, et al.

    Spine deformity 2019; (7(6)):890-898.e4 doi:10.1016/j.jspd.2019.01.011.

    PMID: 31731999
  5. 5

    Spinal growth velocity versus height velocity in predicting curve progression in peri-pubertal girls with idiopathic scoliosis.

    Shi B, Mao S, Liu Z, et al.

    BMC musculoskeletal disorders 2016; (17(1)):368 doi:10.1186/s12891-016-1221-6.

    PMID: 27562617
  6. 6

    Does the Use of Sanders Staging and Distal Radius and Ulna Classification Avoid Mismatches in Growth Assessment with Risser Staging Alone?

    Cheung PWH, Cheung JPY

    Clinical orthopaedics and related research 2021; (479(11)):2516-2530 doi:10.1097/CORR.0000000000001817.

    PMID: 34036944
  7. 7

    The Effect of the Risser Stage on Bracing Outcome in Adolescent Idiopathic Scoliosis.

    Karol LA, Virostek D, Felton K, et al.

    The Journal of bone and joint surgery. American volume 2016; (98(15)):1253-9 doi:10.2106/JBJS.15.01313.

    PMID: 27489315
  8. 8

    Curve Progression in Adolescent Idiopathic Scoliosis with Cobb Angles Between 40 and 50 Degrees at the Late Stage of Skeletal Growth: A Minimum 5-Year Follow-Up Study.

    Nam Y, Patel U, Chang DG, et al.

    Journal of clinical medicine 2025; (14(15)) doi:10.3390/jcm14155272.

    PMID: 40806894
  9. 9

    The relationship of calcaneal apophyseal ossification and Sanders hand scores to the timing of peak height velocity in adolescents.

    Nicholson AD, Sanders JO, Liu RW, Cooperman DR

    The bone & joint journal 2015; (97-B(12)):1710-7 doi:10.1302/0301-620X.97B12.36574.

    PMID: 26637689
  10. 10

    Prediction of Curve Progression in Idiopathic Scoliosis: Validation of the Sanders Skeletal Maturity Staging System.

    Sitoula P, Verma K, Holmes L, et al.

    Spine 2015; (40(13)):1006-13 doi:10.1097/BRS.0000000000000952.

    PMID: 26356067
  11. 11

    Is It Growth or Natural History? Increasing Spinal Deformity After Sanders Stage 7 in Females With AIS.

    Grothaus O, Molina D, Jacobs C, et al.

    Journal of pediatric orthopedics 2020; (40(3)):e176-e181 doi:10.1097/BPO.0000000000001415.

    PMID: 31181026
  12. 12

    Skeletal growth velocity of adolescent idiopathic scoliosis: abnormal in spine but normal in lower limbs.

    Shu S, Gu Q, Zhang T, et al.

    Annals of translational medicine 2020; (8(6)):359 doi:10.21037/atm.2020.02.48.

    PMID: 32355803
  13. 13

    Skeletally Immature Patients With Adolescent Idiopathic Scoliosis Curves 15°-24° Are at High Risk for Progression.

    Zapata KA, Sucato DJ, Lee MC, Jo CH

    Spine deformity 2019; (7(6)):870-874 doi:10.1016/j.jspd.2019.02.012.

    PMID: 31731996
  14. 14

    Curve type, flexibility, correction, and rotation are predictors of curve progression in patients with adolescent idiopathic scoliosis undergoing conservative treatment : a systematic review.

    Wong LPK, Cheung PWH, Cheung JPY

    The bone & joint journal 2022; (104-B(4)):424-432 doi:10.1302/0301-620X.104B4.BJJ-2021-1677.R1.

    PMID: 35360948
  15. 15

    Can curve characteristics predict severe progression in night-time bracing in adolescent idiopathic scoliosis?

    Gross J, Ragborg L, Heegaard M, et al.

    European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 2026; doi:10.1007/s00586-026-09884-3.

    PMID: 41879837
  16. 16

    Discontinuation of brace treatment in adolescent idiopathic scoliosis (AIS): a scoping review.

    Swaby L, Cui M, Cole A

    Spine deformity 2024; (12(5)):1217-1228 doi:10.1007/s43390-024-00882-3.

    PMID: 38693334
  17. 17

    Effect of curve location on the severity index for adolescent idiopathic scoliosis: a longitudinal cohort study.

    Vergari C, Skalli W, Abelin-Genevois K, et al.

    European radiology 2021; (31(11)):8488-8497 doi:10.1007/s00330-021-07944-4.

    PMID: 33884474

This page explains how doctors estimate scoliosis progression during growth for informational purposes only and does not constitute medical advice. Your spine specialist should interpret your X-rays, maturity scores, and Cobb angle and recommend follow-up or treatment for your situation.

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