Do bones get bigger after 18? A look at adolescent and adult bone growth

By age 18, most people have achieved about 90% of their adult height, as the cartilage in their growth plates begins to close and harden. However, the question of whether bones get bigger after 18 is more nuanced than a simple 'no,' as different types of bone growth and remodeling continue well into adulthood.

Quick Summary

Long bones typically stop lengthening in the late teens due to the closure of growth plates, but bones can still grow in width through appositional growth. Bone density and mass also continue to increase until the late 20s or early 30s, and bone remodeling is a lifelong process influenced by diet and exercise.

Key Points

• Height growth stops after 18: Linear bone growth, responsible for height, ceases when growth plates at the ends of long bones fuse, typically by the end of adolescence.

• Bones continue to grow in width: Through a process called appositional growth, bones can increase in diameter throughout life in response to physical stress and increased muscle activity.

• Peak bone mass is reached later: While linear growth stops in the late teens, bone density and mass continue to increase slowly, reaching their peak between the ages of 25 and 30.

• Exercise impacts bone width and density: Weight-bearing and resistance exercises stimulate the growth of new bone tissue, strengthening bones and increasing density, even after age 18.

• Bones are always remodeling: The skeleton is a dynamic tissue, constantly being broken down and rebuilt in a process called remodeling, which is crucial for repair and adaptation throughout life.

• Lifestyle influences bone health: Proper nutrition, including sufficient calcium and vitamin D, and regular exercise are essential for maximizing peak bone mass and slowing bone loss with age.

Understanding the cessation of bone lengthening

For most individuals, growth in height comes to a halt during the late teenage years, specifically between 16 and 18 for women and 18 and 21 for men. This process is dictated by the epiphyseal plates, or growth plates, which are areas of specialized cartilage found at the ends of long bones. Throughout childhood and adolescence, these plates produce new bone tissue, causing the bones to lengthen. As puberty concludes, hormonal changes cause the growth plates to ossify, or harden, fusing with the main part of the bone. Once this fusion is complete, linear bone growth is no longer possible.

The process of epiphyseal plate closure

• Cartilage production slows: The rate of cartilage cell division at the growth plates decreases as puberty progresses.
• Ossification accelerates: Osteoblasts, the cells responsible for bone formation, begin to replace the remaining cartilage with solid bone.
• Plate fuses: The epiphysis (end of the bone) and the diaphysis (main shaft) unite, leaving a visible epiphyseal line.
• Growth ceases: With the growth plate gone, no further increase in bone length can occur.

Appositional growth: The continued widening of bones

While long bones cannot get longer after the growth plates have closed, they can still grow in thickness or diameter. This process, known as appositional growth, continues throughout life and is a response to the stresses placed on the bones. Osteoblasts on the outer surface of the bone lay down new bone tissue, while osteoclasts on the inner surface break down old bone. This mechanism prevents the bones from becoming excessively heavy and bulky while simultaneously increasing their strength to support increased muscle activity or body weight.

Research has provided surprising evidence of this lifelong process. A 2011 study published in the Journal of Orthopaedic Research found that the pelvic bones of both men and women continued to widen well into old age, long after skeletal maturity was reached. This study challenged the previous assumption that such widening was solely due to an increase in body fat, demonstrating that the bone structure itself was changing.

Bone mineral density vs. bone size

When people ask, "do bones get bigger after 18?," they are often concerned about overall bone strength, which is measured by bone mineral density (BMD) and mass, not just size. While peak bone mass is typically reached between the ages of 25 and 30, it continues to increase slowly until then. Maximizing this peak bone mass during youth and early adulthood is a critical factor in protecting against osteoporosis later in life. The bone consolidation phase in the late teens is particularly important, as roughly 10% of total bone mass is still accumulating after height growth ceases.

The crucial role of lifestyle choices

Even after skeletal maturity, lifestyle factors continue to play a vital role in maintaining bone health. As you age, the process of bone remodeling—where old bone tissue is broken down and replaced with new—can become imbalanced, leading to a net loss of bone mass. Proper nutrition and exercise are essential for keeping this process healthy and minimizing age-related bone loss.

Aspect	Bone Growth in Adolescence	Bone Growth After 18
Linear Growth	Lengthens significantly via epiphyseal plates.	Stops as growth plates fuse and ossify.
Appositional Growth	Increases bone diameter, primarily in response to physical stress.	Continues throughout life, thickening bones in response to load.
Bone Mass	Rapid accumulation, with 40-60% of peak bone mass acquired during puberty.	Consolidates until late 20s or early 30s, followed by gradual decline.
Remodeling	Rapid and efficient, renewing the entire skeleton in about two years.	Slower process, taking 7-10 years to renew the skeleton.
Effect of Exercise	Maximize peak bone mass through weight-bearing activities.	Slows bone loss and maintains density.

Conclusion

In summary, while the long bones that determine height stop growing after the growth plates close in the late teens, the idea that bones stop changing after 18 is a misconception. Bones continue to grow in width through appositional growth in response to mechanical stress and continue to gain density into the late 20s or early 30s. This ongoing bone remodeling process means that maintaining a healthy lifestyle with adequate calcium, vitamin D, and weight-bearing exercise is crucial for building and preserving strong bones throughout adulthood. The foundation for lifelong bone health is built during youth, but positive habits can continue to fortify your skeleton for decades to come.

For more comprehensive information on lifelong bone health, the American Academy of Orthopaedic Surgeons provides an excellent resource on healthy bones at every age.

Frequently Asked Questions

Can adults still gain height after age 18?

For most people, height gain stops after age 18 because the growth plates in their bones fuse and ossify, preventing any further lengthening.

Does weightlifting make your bones bigger?

Weightlifting and other weight-bearing exercises can make your bones denser and thicker in response to the stress placed upon them, but they do not increase bone length.

When does peak bone mass occur?

Peak bone mass, the maximum bone strength and density an individual can achieve, is typically reached between the ages of 25 and 30.

How can I improve my bone density after 18?

To improve bone density after 18, engage in weight-bearing exercises like walking, running, and weightlifting, ensure adequate calcium and vitamin D intake, and avoid excessive alcohol or smoking.

Do all bones stop growing at the same time?

No, bone growth is not uniform across the skeleton. Different bones, and different parts of the same bone, grow and mature at varying rates throughout childhood and adolescence.

What is the difference between linear growth and appositional growth?

Linear growth is the lengthening of long bones, which ceases after the growth plates close. Appositional growth is the increase in bone diameter or width, which continues throughout life.

Can pelvic bones continue to grow after skeletal maturity?

Yes, research indicates that the pelvis can continue to widen throughout adulthood in both men and women, with some studies finding a significant increase in width up to age 80.