What is a Bone Test for Age? Understanding the Science of Skeletal Maturity

Oct 25, 2025 4 min read •

Medical Science Pediatrics Forensic Science

According to research from Johns Hopkins Medicine, bone density tests can help predict a person's risk for fractures by measuring mineral content in the bones. A bone test for age, or skeletal age assessment, uses similar radiological methods for different purposes, including evaluating a child's development or estimating an individual's age in forensic contexts.

Quick Summary

A bone test for age uses radiological imaging like X-rays to assess skeletal maturity and mineralization. In children, it involves comparing images of growth plates to standard atlases. In adults and forensic cases, methods focus on factors like bone density, fusion of epiphyses, and dental development.

Key Points

Pediatric Bone Age Test: Measures a child's skeletal maturity by comparing an X-ray of their hand and wrist to a standard atlas, assessing the stage of development.
Forensic Age Estimation: In forensic science, age is estimated from skeletal remains or a living person by analyzing epiphyseal fusion, dental development, and degenerative changes.
Bone Density (DXA) Scan: This is a different test used primarily for adults to measure bone mineral density and assess the risk of osteoporosis, not to determine chronological age.
Growth Plates: In children, bone age is determined by examining growth plates (epiphyses), which are softer, less mineralized areas at the ends of long bones that eventually close as the child matures.
Multiple Indicators in Forensics: Experts use a range of indicators, including the fusion of the clavicle, dental mineralization, and changes to the pelvis, to improve accuracy in forensic age estimation.
Results Vary: Factors like genetics, nutrition, and overall health can cause a person's bone age to differ from their chronological age, a variability accounted for by experts.

What is a Bone Age Test for Children?

For children, a bone test for age is officially known as a skeletal maturity assessment. A low-dose X-ray of the left hand and wrist is typically taken and compared to standardized reference atlases, such as the Greulich-Pyle atlas. This test measures a child's biological and structural maturity, which can be different from their chronological age. This divergence can be influenced by factors like genetics, nutrition, and medical conditions.

Radiologists examine the bones in the hand and wrist because this area contains numerous growth centers and is easy to image with minimal radiation exposure. They look for specific features, including:

The appearance and shape of carpal bones.
The development and mineralization of epiphyses (the ends of long bones).
The condition of growth plates, which are visible as darker lines on X-rays until they fuse.

Pediatricians and endocrinologists use these tests to diagnose and monitor growth disorders, predict a child’s final adult height, and determine the optimal timing for hormone therapies if needed.

How is a Bone Test Used in Forensic Science?

In forensic contexts, a bone test for age is used to estimate the age of deceased individuals whose identities are unknown or to verify the age of living persons in medicolegal situations. Unlike pediatric assessments, forensic methods must account for the cessation of growth in adulthood and the degenerative changes that occur over a lifetime.

Forensic anthropologists rely on several indicators when analyzing skeletal remains:

Epiphyseal Fusion: They assess the fusion of growth plates, particularly those that are the last to fuse, such as the clavicle (collarbone). In forensic cases, the medial end of the clavicle can be used to estimate age in individuals aged 18 to 22.
Dental Development: The mineralization of teeth and the eruption of permanent dentition, including third molars (wisdom teeth), are highly reliable indicators of age in younger individuals. Even in adults, the ratio of tooth size to dental pulp can provide useful information.
Degenerative Changes: For older adults, age can be estimated by examining degenerative changes in the skeleton. This includes the metamorphosis of the pubic symphysis, changes to the auricular surface of the pelvis, and the extent of cranial suture closure.

Comparison Table: Pediatric Bone Age vs. Adult Forensic Estimation


Feature	Pediatric Bone Age Assessment	Adult Forensic Age Estimation
Primary Goal	Assess skeletal maturation and predict future growth.	Estimate chronological age of a deceased or living individual for identification.
Skeletal Areas Examined	Typically a single X-ray of the left hand and wrist.	Varies, can include teeth, clavicle, pubic symphysis, and auricular surface.
Key Indicators	Presence and fusion of growth plates (epiphyses), shape of carpal bones.	Epiphyseal fusion (especially clavicle), dental formation, degenerative changes.
Underlying Principle	Growth and development follow predictable patterns.	Degeneration and wear of bones occur predictably over time.
Reference Materials	Standardized atlases like Greulich-Pyle and Tanner-Whitehouse.	Forensic data from documented skeletal collections and statistical models.

The Role of Bone Density Scans

While often confused with a bone age test, a bone density test, or DXA scan, serves a different purpose. It measures bone mineral density (BMD) to assess bone strength and the risk of fractures. This is primarily used to diagnose osteopenia or osteoporosis, conditions where bones become weak and brittle. While bone density naturally decreases with age, the test itself is not used to determine an individual's chronological age but rather to evaluate their risk for age-related bone diseases.

Conclusion

A bone test for age is not a single procedure but a set of distinct radiological techniques used for different age groups and applications. In children, it assesses biological maturity by analyzing growth patterns in hand and wrist X-rays, aiding pediatricians in managing growth-related conditions. For forensic purposes, experts use a combination of skeletal and dental indicators to provide an age estimate. It's important to distinguish these diagnostic and forensic tests from a bone density (DXA) scan, which evaluates bone strength and risk of fracture, a concern more prevalent in older adults. Each type of bone test provides crucial information tailored to a specific medical or legal context. For more information on bone health, consult resources from reputable medical institutions like Johns Hopkins Medicine.

Additional Age Estimation Methods

Radiography of other sites: In addition to the hand and wrist, some methods also use X-rays of the knee, elbow, and cervical vertebrae for bone age assessment in children and adolescents.
Dental X-rays: Forensic dentists use dental development stages, such as the mineralization and eruption of teeth, as a reliable method for age estimation, particularly for younger individuals.
Histology: This involves the microscopic examination of bone tissue. Analyzing features like the number of osteons (microscopic bone structures) can provide age-related data, particularly in adults.
Biochemical Analysis: Cutting-edge forensic methods explore biochemical markers within bone and dental tissue, such as the racemization of aspartic acid, to offer more precise age estimations.

These diverse approaches highlight the complexity of estimating age from skeletal remains and the ongoing advancements in medical and forensic science to refine these techniques.

The Importance of Context

Regardless of the method, it's crucial to remember that bone age assessments and forensic estimations are subject to various factors that can affect their accuracy. Population variations, nutritional status, and individual health all play a role in skeletal development and degeneration. For this reason, results are typically reported as a range, and interpretation should always be done by a trained expert who can account for these contextual variables.

Frequently Asked Questions

For children, bone age tests are highly accurate when conducted by qualified professionals using standard imaging techniques and atlases. In forensic cases involving adults, age estimations are less precise and are typically given as a range, relying on multiple skeletal indicators to increase reliability.

A bone density test (DXA scan) measures the mineralization and strength of bones to screen for osteoporosis, a disease causing brittle bones. A bone age test, conversely, assesses a child's skeletal maturity or, in forensics, estimates chronological age based on developmental or degenerative bone changes.

The hand and wrist are used because they contain numerous growth centers (growth plates), providing a comprehensive view of skeletal development from a single X-ray. It also requires minimal radiation exposure, making it a safe procedure for children.

If a child's bone age is younger, it suggests delayed skeletal development. This can be a normal variation or may indicate a medical condition such as a growth hormone deficiency, hypothyroidism, or constitutional growth delay.

An older bone age indicates accelerated skeletal maturation, which could be a sign of conditions like early (precocious) puberty or adrenal gland disorders. It is also a factor considered when predicting final adult height.

Yes, in forensic anthropology, skeletal remains from adults are analyzed to estimate age at death. Unlike children's tests that focus on growth, these methods examine degenerative changes, such as the fusion of late-maturing growth plates (e.g., the clavicle) and changes to the pelvis.

Yes, dental development is a valuable tool for age estimation, particularly in younger individuals, and is a common technique in forensic dentistry. It involves assessing the calcification and eruption stages of teeth via radiographs.

References

Medical Disclaimer

This content is for informational purposes only and should not replace professional medical advice. Always consult a qualified healthcare provider regarding personal health decisions.