What Is the Risser Sign, and How Is Skeletal Maturity Measured?
The Risser sign is a grading system that estimates how much spinal growth a young person has left. It works by looking at the bony cap (apophysis) on the top of the pelvis on an X-ray. Graded from 0 to 5, a higher number means less remaining growth. Clinicians use it to guide monitoring and treatment decisions for scoliosis.
Key takeaways
- The Risser sign grades skeletal maturity from 0 (still growing) to 5 (growth complete).
- It is measured from a standard pelvis X-ray, looking at the iliac crest apophysis.
- Low Risser grades carry a higher risk of curve progression in scoliosis.
- Sanders staging of the hand and wrist offers a more detailed view of growth remaining.
- Standing, weight-bearing imaging captures the pelvis and spine under real loading conditions.
How does the Risser sign work?
The Risser sign works by tracking a strip of cartilage along the top rim of the pelvis, called the iliac apophysis. During adolescence this cartilage gradually turns to bone, moving from the outer hip towards the spine. A radiographer or radiologist looks at this strip on an X-ray and assigns a grade from 0 to 5 based on how far the ossification has progressed and whether it has fused to the pelvis.
Because the pelvis is almost always visible on a full-spine X-ray, the Risser sign can be assessed at the same time as a Cobb angle measurement, without needing a separate scan.
What do the Risser grades mean?
Each Risser grade describes a specific stage of pelvic bone maturity. The higher the grade, the less growth remains.
No ossification visible. The skeleton is still in an early growth phase. Curve progression risk is highest at this stage.
Ossification covers the outer quarter of the iliac crest. Significant growth still remains.
Ossification reaches the halfway point. Growth is slowing but the skeleton is not yet mature.
Ossification covers three quarters of the crest. Most rapid growth has passed, but some remains.
The apophysis runs the full length of the crest but has not yet fused to the pelvis. Minimal growth left.
Complete fusion. Skeletal growth is considered finished. Curve progression risk is much lower.
What is Sanders staging and how does it compare to the Risser sign?
Sanders staging is a newer classification that uses a hand and wrist X-ray to assess bone age in more detail. It divides skeletal maturity into eight stages, giving clinicians finer resolution during the rapid growth phase when curve progression risk is greatest.
The Risser sign is useful but somewhat broad. A patient can sit at Risser 0 for a long stretch, during which time a scoliosis curve may change significantly. Sanders staging helps pinpoint exactly where in the growth spurt the patient is, making it easier to decide whether bracing, closer monitoring, or watchful waiting is appropriate.
In practice, many specialists use both systems together. A spinal X-ray provides the Risser grade and Cobb angle measurement, while a separate hand X-ray provides the Sanders stage.
What it looks at: The bony cap on the pelvis (iliac crest apophysis).
Scale: 0 to 5.
Strength: Easy to read from a standard spine or pelvis X-ray. Widely understood by clinicians.
Limitation: Less precise during the fastest growth period (Risser 0 to 1).
What it looks at: The growth plates in the hand and wrist bones.
Scale: 1 to 8.
Strength: Finer detail during peak growth, helping to predict curve behaviour more precisely.
Limitation: Requires a separate hand X-ray. Less widely used outside specialist scoliosis centres.
Why does skeletal maturity matter for scoliosis?
Skeletal maturity matters because a spine that is still growing is at far greater risk of a scoliosis curve getting worse. The more growth remaining, the more time the curve has to progress. That is why clinicians check skeletal maturity at every monitoring appointment.
A low Risser grade combined with a larger curve is a strong signal that intervention, usually bracing, may be needed to slow or prevent progression. A high Risser grade with a stable curve often means the patient can be monitored less frequently or discharged from active monitoring altogether.
- Risser 0 or 1
- Larger curve size
- Before or during the growth spurt
- Sanders stage 1 to 3
- Risser 4 or 5
- Smaller, stable curve
- Growth spurt already passed
- Sanders stage 7 or 8
When is MRI more appropriate? The Risser sign and Cobb angle are measured on X-ray, which shows bones, joints and alignment clearly. If there is concern about the spinal cord, nerves or discs, for instance with unusual pain, rapid progression or neurological symptoms, MRI is usually the better tool because it shows soft tissue in detail.
How does standing imaging help with skeletal maturity assessment?
Standing, weight-bearing imaging captures the spine and pelvis exactly as they behave when a person is upright. When you lie down for a conventional scan, gravity is removed, muscles relax, and curves can appear smaller than they truly are. A standing X-ray shows the real load on the skeleton and gives the most accurate view of both the curve and the Risser sign in one image.
At ScanAlign, low dose standing imaging, full-length standing scans use about 90% less radiation than a standard X-ray, around ten times less. For a condition that needs repeat monitoring over months or years, keeping the radiation dose as low as possible matters.
If you have a scoliosis monitoring report that mentions the Risser sign and you want to understand what it means for your next steps, a free video consultation can help you decide whether a standing scan is right for you.
Book a free video consultationFrequently asked questions about the Risser sign
Risser 0 means no ossification is visible along the iliac crest. The skeleton is still in an early growth phase, which means there is a higher risk that a scoliosis curve could progress. Closer monitoring is usually recommended at this stage.
At Risser 3, the most rapid growth has usually passed, but some growth remains. Curves may still change, so monitoring typically continues until the Risser grade reaches 4 or 5.
Scoliosis monitoring is the most common use. However, orthopaedic surgeons also consider skeletal maturity for other growth-related conditions and for timing surgical procedures.
MRI shows soft tissue best. The Risser sign is assessed on a plain X-ray because it relies on seeing bone ossification clearly. An MRI of the pelvis may show the apophysis, but X-ray remains the standard method.
The Risser sign looks at the pelvis and uses a 0 to 5 scale. Sanders staging looks at the hand and wrist and uses a 1 to 8 scale. Sanders gives more detail during rapid growth phases, while the Risser sign is more widely used and can be read from any standard spine X-ray.
Your specialist will set the monitoring schedule based on your curve size and growth stage. It is typically every four to six months during peak growth, though this varies from person to person.
The Risser grade itself does not change between standing and lying down, because it measures bone maturation rather than alignment. However, a standing X-ray gives a more accurate picture of the scoliosis curve at the same time, which is important when the Risser grade and curve are assessed together.
No. ScanAlign offers self-referred appointments for adults. You can book a free video consultation to discuss whether a standing scan is appropriate for your situation.
The EOS system used at ScanAlign delivers about 90% less radiation than a standard X-ray, around ten times less. This is especially important when repeated scans are needed over time.
Pricing details are available on the ScanAlign FAQs page. A free video consultation before booking helps confirm the right scan for your needs.
Understand your Risser grade in context
A free video consultation with our team can help you understand your report, assess whether a standing scan would add useful information, and plan your next steps.
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- Risser JC. The iliac apophysis: an invaluable sign in the management of scoliosis. Clinical Orthopaedics and Related Research. 1958;11:111-119.
- Sanders JO et al. Maturity assessment and curve progression in girls with idiopathic scoliosis. Journal of Bone and Joint Surgery (American). 2007;89(1):64-73.
- Scoliosis Research Society. Patient information: skeletal maturity and scoliosis. srs.org.
Written by Abbas Dhami (Specialist Diagnostic Radiographer)
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.