Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis in patients between the ages of 10 and 18 years.1 Scoliosis is defined as a lateral curvature >10°.1 Girls are 10 times more likely to have curvatures of >30° and are more likely to have a progressive deformity.1

AIS is best managed based on the severity of the spinal curve and the likelihood of curve progression. The best predictors of whether the curve will progress are the amount of residual skeletal growth and the curve magnitude. The Risser classification scale uses the stages of iliac crest apophyseal ossification to grade skeletal maturity. There are 6 stages of classification2:

  • Stage 0: No ossification center at the level of the iliac crest apophysis
  • Stage 1: Apophysis <25% of iliac crest
  • Stage 2: Apophysis 25% to 50% of iliac crest
  • Stage 3: Apophysis 50% to 75% of iliac crest
  • Stage 4: Apophysis >75% of iliac crest
  • Stage 5: Complete ossification and fusion of the iliac crest apophysis.

Patients at a lower Risser stage have a higher incidence of curve progression. For example, patients at Risser stage 0 to 1 with a Cobb angle between 5° and 19° have a 22% likelihood of curve progression, while patients at Risser stage 0 to 1 with a Cobb angle between 20° and 29°  have a 68% incidence of curve progression.3 By contrast, patients at Risser stages 2, 3, and 4 with a Cobb angle between 5° and 19° have a 1.6% incidence of curve progression; patients with a Cobb angle between 20° and 29° have a 23% incidence of curve progression.3

Family history and rotational prominence do not correlate with the incidence of curve progression. Thoracic curvatures are more likely to progress compared with lumbar curvatures.1 Physical examination findings of scoliosis include shoulder elevation, iliac crest height asymmetry, limb length inequality, and rib rotational deformity.1,3 In most cases, AIS will not progress to the point where bracing or surgery is necessary.1

Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.


1. Souder C. Adolescent idiopathic scoliosis. OrthoBullets website. Updated January 26, 2020. Accessed May 18, 2020.

2. Hacquebord JH, Leopold SS. In brief: the Risser classification: a classic tool for the clinician treating adolescent idiopathic scoliosis. Clin Orthop Relat Res. 2012;470(8):2335-2338.

3. Lonstein JE, Carlson JM. The prediction of curve progression in untreated idiopathic scoliosis during growth. J Bone Joint Surg Am. 1984;66(7):1061-1071.

Loading Quiz...