Analyzing Bone Age Xray Images: Growth Plates

A bone age X-ray is one of the most useful tools for understanding a child's skeletal development and remaining growth potential.

Parents often encounter bone age testing after asking questions such as:

Why is my child shorter than expected?

Is my teenager a late bloomer?

How much longer does my child have to grow?

Are the growth plates still open?

Could delayed puberty be affecting height?

Unlike chronological age—which simply tells us how many years a child has been alive—bone age estimates how mature the skeleton appears.

A child who is chronologically 14 years old does not necessarily have a bone age of 14.

Their skeleton may appear younger, approximately the same age, or more mature than expected.

That difference can provide valuable information about puberty, growth timing, growth disorders, and how much height may potentially remain.

This guide explains what a bone age X-ray is, how a bone age study is performed, why the hand and wrist are used, how bone age X-ray images are interpreted, and what delayed or advanced bone age may mean for a child's future growth.

What Is a Bone Age X-Ray?

A bone age X-ray is a radiographic study used to estimate the maturity of a child's skeleton.

It is typically performed using an X-ray of the left hand and wrist.[1,2]

The resulting image allows clinicians and radiologists to examine the development of numerous bones and growth centers at the same time.

The child's skeletal appearance is then compared with established standards to estimate a skeletal—or bone—age.

For example:

Chronological age: 13 years

Bone age: 11 years

This would indicate that skeletal development appears delayed relative to chronological age.

Alternatively:

Chronological age: 13 years

Bone age: 14 years

This would indicate more advanced skeletal maturation.

Neither finding automatically indicates a medical disorder. Bone age must always be interpreted alongside the child's growth history, puberty stage, family history, and overall health.

What Is Bone Age?

Bone age is an estimate of skeletal maturity.

Chronological age measures time since birth.

Bone age evaluates how far the skeleton has progressed through its developmental process.

During childhood and adolescence, bones change in predictable ways.

Growth centers enlarge, bones develop their mature shape, and the growth plates progressively narrow before eventually fusing.

These changes can be observed on X-ray.

Because skeletal maturation is closely connected with growth and puberty, bone age provides information that chronological age alone cannot.

Why Is Bone Age Important?

Bone age can help answer several clinically important questions.

A bone age study X-ray may help evaluate:

• Remaining growth potential
• Delayed growth
• Advanced growth
• Puberty timing
• Delayed puberty
• Delayed bone age
• Short stature
• Growth plate maturation
• Predicted adult height
• Certain endocrine disorders

It is especially useful when a child's physical development does not appear to match their chronological age.

Why Is a Hand X-Ray Used for Bone Age?

The standard hand X-ray for bone age typically includes the left hand and wrist.

There is a good reason for this.

The hand and wrist contain many bones and growth centers that mature at different points during childhood and adolescence.

A single image can show the:

• Phalanges
• Metacarpals
• Carpal bones
• Radius
• Ulna
• Multiple growth plates

Together, these provide a detailed picture of skeletal development.[1]

This makes a bone age hand and wrist X-ray particularly useful for estimating overall skeletal maturity.

Bone Age Hand and Wrist X-Ray: What Does It Show?

During early childhood, many bones in the hand and wrist are still developing.

As children grow:

• Ossification centers appear
• Bones become larger
• Their shapes change
• Growth plates mature
• Epiphyses progressively approach fusion

By comparing these developmental characteristics with standardized references, clinicians can estimate skeletal age.

This means the X-ray does more than simply show whether one growth plate is open or closed.

It provides a broader picture of the child's overall skeletal maturation.

How Is a Bone Age X-Ray Performed?

The procedure itself is usually quick and straightforward.

Step 1: Positioning the Hand

The child's left hand and wrist are positioned flat on the X-ray surface.

The fingers are typically extended so the bones can be clearly visualized.

Step 2: Taking the X-Ray

A single radiographic image is usually obtained.

The actual image acquisition takes only a moment.

Step 3: Image Review

The resulting bone age X-ray image is reviewed by a radiologist or qualified clinician.

The skeletal features are compared with established bone-age standards.

Step 4: Bone Age Is Estimated

The report may state something such as:

Chronological age: 12 years 6 months

Estimated bone age: 10 years 6 months

The difference is then interpreted within the context of the child's growth and development.

How Should a Child Prepare for a Bone Age X-Ray?

Very little preparation is usually required.

Children typically do not need to:

• Fast
• Change their diet
• Stop normal medications
• Receive contrast
• Undergo sedation

Metal jewelry or objects around the hand and wrist may need to be removed before imaging.

The procedure is generally painless and can usually be completed quickly.

Is a Bone Age X-Ray Safe?

Bone age imaging uses ionizing radiation, but the radiation exposure from a hand/wrist radiograph is low.

As with any medical imaging involving radiation, testing should be performed when clinically appropriate and according to standard radiation-safety principles.

For children being evaluated for abnormal growth or puberty, the potential clinical information from a properly indicated bone age study can be valuable.

What Is a Bone Age Study X-Ray?

The terms bone age X-ray and bone age study X-ray usually refer to the same general evaluation.

A bone age study consists of obtaining an X-ray—usually of the left hand and wrist—and evaluating skeletal maturity.

The important part is not simply taking the image.

The value comes from comparing the child's skeletal development with established standards and interpreting that information alongside their clinical growth pattern.

How Are Bone Age X-Ray Images Interpreted?

There are several established approaches to bone-age interpretation.

Two of the best-known are:

Greulich and Pyle Method

The Greulich and Pyle atlas contains standardized radiographic images representing skeletal development at different ages.

The child's hand and wrist X-ray is compared with reference images to determine which skeletal age it most closely resembles.[1]

This approach is widely used because it is relatively straightforward.

Tanner-Whitehouse Method

The Tanner-Whitehouse method evaluates specific bones individually and assigns maturity scores.

These scores are combined to estimate skeletal age.

It can provide a more systematic assessment but is also more time-consuming.

Modern computer-assisted and automated bone-age systems are also increasingly used to help standardize interpretation.

What Do Doctors Look for on Bone Age X-Ray Images?

Clinicians assess multiple characteristics.

These can include:

Bone Size

Bones increase in size as children mature.

Bone Shape

The appearance and contour of bones change throughout development.

Ossification

Bones progressively become more mineralized and mature.

Epiphyseal Development

The ends of long bones change predictably as skeletal maturity progresses.

Growth Plate Appearance

Growth plates gradually narrow and eventually fuse.

Together, these findings provide an estimate of skeletal maturity.

What Does a Delayed Bone Age Mean?

A delayed bone age means the skeleton appears less mature than expected for chronological age.

For example:

Chronological age: 14

Bone age: 12

This suggests skeletal maturation is approximately two years behind chronological age.

A delayed bone age can sometimes mean the child has more time remaining for growth than chronological age alone would suggest.

However, delayed bone age is not a diagnosis by itself.

What Causes Delayed Bone Age?

Several conditions and normal developmental patterns can result in delayed skeletal maturation.

These include:

Constitutional Growth Delay

Some children are simply late bloomers.

They may:

• Grow later than peers
• Enter puberty later
• Have delayed bone age
• Experience a later growth spurt

Many eventually reach a height appropriate for their genetic potential.

Growth Hormone Deficiency

Children with growth hormone deficiency may have impaired growth velocity and delayed skeletal maturation.

Hypothyroidism

Low thyroid hormone can slow both physical growth and skeletal development.

Nutritional Problems

Inadequate nutrition or certain gastrointestinal disorders can interfere with normal growth.

Chronic Illness

Some chronic medical conditions can delay growth and skeletal maturation.

A delayed bone age therefore needs to be interpreted within the larger clinical picture.

Does Delayed Bone Age Mean More Growth Is Left?

Often, delayed skeletal maturity suggests that additional growth time may remain.

But this does not guarantee a particular number of inches.

For example, two 15-year-old boys could have very different bone ages.

Teenager A

Chronological age: 15
Bone age: 15

Teenager B

Chronological age: 15
Bone age: 13

Teenager B may have a later skeletal-development timeline and potentially more remaining growth.

However, final height still depends on:

• Genetics
• Puberty
• Growth velocity
• Hormonal health
• Nutrition
• Underlying medical conditions

Bone age is one piece of the puzzle—not a precise height forecast.

What Does Advanced Bone Age Mean?

Advanced bone age means the skeleton appears more mature than expected for chronological age.

For example:

Chronological age: 12

Bone age: 14

This may suggest that skeletal maturation is occurring faster than expected.

Advanced bone age can sometimes be associated with:

• Early puberty
• Precocious puberty
• Increased sex hormone exposure
• Certain adrenal hormone conditions
• Other endocrine disorders

An advanced bone age can also mean that the remaining growth window may be shorter than chronological age alone would suggest.

Bone Age and Growth Plates

Bone age is closely connected to growth plate development.

Growth plates—also called physes—are areas of developing cartilage near the ends of long bones.

They allow bones to lengthen during childhood and adolescence.

As skeletal maturity progresses:

1. Growth plates remain wide and active during earlier growth.
2. They gradually narrow.
3. Puberty accelerates skeletal maturation.
4. Growth plates progressively fuse.
5. Once completely fused, normal long-bone lengthening ends.

A bone age X-ray can therefore provide useful information about whether skeletal development is early, intermediate, or approaching maturity.

Can a Bone Age X-Ray Tell If Growth Plates Are Closed?

A hand and wrist X-ray can show the maturity and fusion status of growth plates visible in that region and can help assess overall skeletal maturity.

However, growth plates throughout the body do not necessarily fuse at exactly the same moment.

Therefore, clinicians interpret the entire skeletal pattern rather than relying on a single growth plate.

If the hand and wrist demonstrate advanced skeletal maturity and the teenager has essentially stopped gaining height, this can strongly suggest that remaining linear growth is limited.

Can Bone Age Predict Adult Height?

Bone age can be incorporated into methods that estimate predicted adult height.

Prediction models may consider:

• Bone age
• Current height
• Chronological age
• Sex
• Parental height
• Pubertal development

These calculations can be useful for counseling families.

However:

Predicted adult height is an estimate—not a guarantee.

Predictions may change as a child progresses through puberty, particularly if growth or puberty does not follow an average pattern.

Bone Age vs. Chronological Age

Understanding this distinction is one of the most important concepts in pediatric growth.

Chronological Age	Bone Age
Time since birth	Estimated skeletal maturity
Cannot change	Can be delayed, appropriate, or advanced
Does not directly show growth potential	Helps assess remaining skeletal growth
Based on birthday	Based on skeletal development

A child's birthday tells us how old they are.

A bone age study helps tell us where their skeleton is in the growth process.

Bone Age vs. Bone Density X-Ray

These are not the same test.

People sometimes search for a bone density X-ray when they actually mean a bone age study.

Bone Age X-Ray

Evaluates:

• Skeletal maturity
• Growth plate development
• Growth timing
• Remaining growth potential

Usually involves an X-ray of the hand and wrist.

Bone Density Testing

Evaluates:

• Bone mineral density
• Bone strength
• Risk of low bone mass

Bone mineral density is commonly assessed with DXA (dual-energy X-ray absorptiometry) rather than a standard bone-age hand X-ray.

A bone age study therefore does not measure bone density.

When Might a Child Need a Bone Age X-Ray?

A clinician may consider a bone age study when evaluating:

• Short stature
• Poor growth velocity
• Delayed puberty
• Early puberty
• Constitutional growth delay
• Suspected growth hormone deficiency
• Abnormal height progression
• Predicted adult height concerns
• Unusually rapid growth
• Certain endocrine disorders

It may also be useful when parents want to understand whether a teenager's growth pattern is delayed relative to chronological age.

Bone Age and Growth Hormone Evaluation

Bone age is commonly one part of a larger pediatric growth evaluation.

When growth hormone deficiency or another growth disorder is suspected, clinicians may also review:

• Growth charts
• Growth velocity
• Height percentile
• Parental heights
• Puberty stage
• IGF-1
• IGFBP-3
• Thyroid function
• Other laboratory testing when indicated

Bone age alone cannot diagnose growth hormone deficiency.

Similarly, a delayed bone age does not automatically mean a child needs growth hormone treatment.

What Is a Normal Bone Age?

There is natural variation between chronological age and skeletal age.

A small difference does not necessarily indicate a problem.

The significance depends on:

• The size of the difference
• The child's age
• Puberty stage
• Growth velocity
• Height percentile
• Family development patterns
• Clinical symptoms

This is why the result should be interpreted in context rather than treating a bone age number as an isolated diagnosis.

Can Bone Age Change Over Time?

Yes.

Bone age progresses as the skeleton matures.

A child may have another bone age study later if monitoring skeletal development is medically appropriate.

Doctors may compare studies to determine whether bone maturation is:

• Progressing normally
• Remaining delayed
• Advancing rapidly
• Approaching skeletal maturity

Repeat imaging is not automatically necessary for every child and should be based on the clinical situation.

How Accurate Is a Bone Age X-Ray?

Bone age is useful, but it is still an estimate.

Interpretation can vary depending on:

• The method used
• Image quality
• The child's developmental pattern
• Reader experience
• Population differences
• Underlying medical conditions

Research has also identified variability between readers using traditional bone-age methods.[2,3]

For this reason, a bone age result should not be interpreted as an exact biological clock.

It is best viewed as one important measurement within a broader growth assessment.

Can You Determine Bone Age Without an X-Ray?

Physical development can provide clues about skeletal maturity, but it cannot precisely determine bone age.

Factors such as:

• Puberty stage
• Menstrual history
• Facial hair
• Voice changes
• Shoe size
• Recent growth

may suggest where someone is developmentally.

However, these do not replace skeletal imaging when an actual bone age assessment is clinically needed.

The Bottom Line

A bone age X-ray is one of the most useful tools available for evaluating skeletal development in children and teenagers.

Unlike chronological age, bone age provides information about how mature the skeleton actually is.

A standard bone age hand and wrist X-ray can help clinicians evaluate:

• Skeletal maturity
• Growth plate development
• Delayed or advanced development
• Puberty timing
• Remaining growth potential
• Predicted adult height
• Possible growth disorders

A delayed bone age may suggest that a child has more developmental time remaining, while an advanced bone age can indicate that skeletal maturation is progressing more quickly.

However, bone age should never be interpreted by itself.

The most accurate assessment combines the X-ray with:

• Growth velocity
• Height percentile
• Family height
• Puberty stage
• Medical history
• Laboratory testing when appropriate

Ultimately, the most useful question is not simply:

“What is my child's bone age?”

It is:

“What does this bone age mean when we combine it with the rest of my child's growth pattern?”

That is where a bone age study becomes most valuable.

Concerned About Your Child's Bone Age or Growth Potential?

If your child is growing more slowly than expected, experiencing delayed puberty, falling on their growth chart, or you are uncertain how much growth remains, a comprehensive pediatric growth evaluation can help put a bone age result into context.

At HGH for Children, growth evaluations may consider:

• Growth velocity
• Height percentile
• Family height
• Puberty timing
• Bone age
• Growth plate maturity
• IGF-1
• Growth hormone deficiency
• Predicted adult height
• Remaining growth potential

The goal is not simply to obtain an X-ray. It is to understand what the child's skeletal development means for their overall growth pattern and whether further evaluation is appropriate.

Medically Reviewed By

Dr. Devin Stone, ND

Dr. Devin Stone, ND is a licensed naturopathic doctor and founder of HGHforChildren.com. His clinical focus includes pediatric growth evaluation, short stature assessment, delayed puberty, bone age analysis, growth hormone deficiency screening, IGF-1 interpretation, skeletal maturity assessment, and individualized growth planning for children and adolescents.

Through HGHforChildren.com, Dr. Stone educates families about childhood growth patterns, bone age, growth velocity, growth plate development, height prediction, puberty, and treatment options when medically appropriate.

Medical References

1. Greulich WW, Pyle SI. Radiographic Atlas of Skeletal Development of the Hand and Wrist. Stanford University Press.
The classic reference atlas used for radiographic assessment of skeletal maturity from hand and wrist X-rays.

2. Satoh M. Bone age: assessment methods and clinical applications. Clinical Pediatric Endocrinology. 2015;24(4):143–152. doi:10.1297/cpe.24.143.
Reviews the major methods of bone-age assessment, clinical applications, skeletal maturity, and limitations of bone-age interpretation.

3. Martin DD, Wit JM, Hochberg Z, et al. The use of bone age in clinical practice—Part 1. Hormone Research in Paediatrics. 2011;76(1):1–9.
Reviews clinical applications and interpretation of bone age in children with growth and pubertal concerns.

4. Martin DD, Wit JM, Hochberg Z, et al. The use of bone age in clinical practice—Part 2. Hormone Research in Paediatrics. 2011;76(1):10–16.
Discusses the role of bone age in growth prediction and the limitations that should be considered when interpreting skeletal maturity.

5. Creo AL, Schwenk WF II. Bone age: a handy tool for pediatric providers. Pediatrics. 2017;140(6).
Reviews how bone age is used in pediatric practice to assess growth, puberty, skeletal maturation, and disorders affecting childhood development.

6. Collett-Solberg PF, Ambler G, Backeljauw PF, et al. Diagnosis, genetics, and therapy of short stature in children: a Growth Hormone Research Society International Perspective. Hormone Research in Paediatrics. 2019;92(1):1–14.
Provides an international clinical perspective on short stature, growth assessment, growth velocity, bone age, and endocrine evaluation.