Spine · Conditions

Kyphosis: Definition, Causes, Risk Factors, and Complications

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Kyphosis: Definition

Kyphosis is the medical term for "hunchback." It happens when the upper portion of the spine (the thoracic) region is abnormally curved forward. Some forward curvature in this region is normal, but if the curve is greater than 50 degrees the condition is considered to be "kyphotic" which is abnormal.

A common kyphosis definition states that kyphosis is a forward, exaggerated rounding or curvature of the back, usually the upper thoracic part of the spine which creates the appearance of a hunchback.

Kyphosis is most common among elderly women. However, it can affect anyone, regardless of their age. Its occurrence among elderly women is often a result of osteoporosis weakening their spinal bones, so much so that they compress and crack.

In instances where kyphosis affects a younger person, it is usually as a result of developmental problems, spine trauma and degenerative diseases like arthritis. Unlike severe cases of kyphosis that are often painful and sometimes can cause disfiguration of the back, mild kyphosis causes few manageable problems.

One interesting fact about the spine is that it’s made of a series of ordinary curves that play an important role of absorbing the weight that the body exerts on the spine. The cervical spine curves a little inward, the thoracic spine outward and lumbar bends inwards. Although the lower part of the spine carries most of the body’s weight, all the parts rely on each other to function normally.

Additionally, the curves make it possible for the head of a normal person to stay at a balance directly over their pelvis. However, the head may stay out of balance if the curves of the spine are abnormal. This can result in stiffness, changes in posture or walking pattern problems and back pain.

Scheuermann’s kyphosis, also known as developmental kyphosis is a form of kyphosis which happens during the developmental stages of a person. This condition is caused by stiffness in the vertebrae. At times, Scheuermann's disease adds extra abnormalities, known as Schmoll's nodes to the affected part of the vertebrae. Spine specialists say that the disease thickens and tightens the anterior longitudinal ligament, leading to spinal deformity.

The thickened ligament can have an effect on the growth of the vertebrae in young children and causes an imbalance in its growth. In most cases, there is less growth in the front of the vertebrae and too much on its back. As a result, a wedged vertebrae forms.

When viewed from the front, the spine has a straight look. However, there are some spines that can still show an abnormal curve even when viewed from the front. This condition can be caused by abnormalities of the spine during birth, growth abnormalities in the adolescence stage, unusual vertebrae twisting caused by muscle spasms, especially after an injury, and degenerative spinal changes that occur in adulthood.

Generally, any kyphosis definition has to include the rounding of the back. However, it is important to note that not all cases of a curved upper back are abnormal. Therefore, a good definition must emphasize the exaggerated nature of such a curve.


Kyphosis is thought to affect men and women equally, although this has been debated in some literature. The disorder affects approximately 4 to 8% of the overall population. However, we’ve also seen that kyphosis affects women more than men, specifically elderly women. Therefore, this is an important aspect of the condition, thus the reason why we include it when wecdefine kyphosis.

Postural round back, or hyperkyphosis, is very prevalent in the western societies. Statistics show that the condition, which is very common, affects 15.3% of all Americans. It is also estimated that close to 40% of the elderly have hyperkyphosis, and are also at a higher risk of developing more adverse symptoms related to kyphosis. The prevalence of this condition increases with age, and the greatest change in curvature happens among women aged between 50 to 59 years.

A research conducted to determine the prevalence of kyphosis among school-aged children revealed that kyphosis mostly affected children attending private schools. The main cause of kyphosis among these children was the weight of their school bags.

The statistics showed that 36.9% of public school students and 55.1% of private school students carried backpacks which were not commensurate to their weight. The researchers concluded that there was a significant relationship between the standard weight of a backpack and the prevalence of kyphosis among students.

Regarding the relationship between kyphosis and gender, kyphosis is known to be more prevalent in women than in men. However, there is conflicting data regarding this relationship, as some studies have indicated that more men suffer from kyphosis than women. The researchers stated that the lower prevalence of kyphosis in women was because their working hours were 20% less compared to men. The study showed a significant relationship between gender, working hours and kyphosis.

However, there is a very high prevalence of kyphosis among women. Statistics show that 35% of all women aged between 20 and 60 years have kyphosis. There is also a substantial relationship between upright postural kyphosis and normal postural kyphosis index. In the case of postmenopausal women, normal postural kyphosis is said to be inversely connected to age. So, both upright postural kyphosis and normal postural kyphosis are not related to age in postmenopausal women.

Scheuermann’s kyphosis is prevalent in young people, especially teenagers. It is estimated that this condition affects around 8% of the population in the United States. In Europe, Scheuermann's kyphosis is said to affect 8% of people above the age of 50.

Some in the scientific community define kyphosis by including its prevalence and symptoms. One of the lesser known cause of kyphosis is genetic disorders. The most common kyphosis caused by genetic disorders is congenital kyphosis. It is caused by abnormal vertebral development during pregnancy and it is normally identified after the child has been born. The prevalence of congenital kyphosis is very low, happening once for every 2000 births.

Risk factors

Spinal kyphosis is a disorder which can occur at any stage of life, but it is rarely seen at birth. In adolescents, the disease is also called Scheuermann's disease, and the causes of the condition, or what increases the risk of developing it, are unknown.

In adults, many different conditions can lead to the development of kyphosis, and each of these different causative conditions has their own risk factors.

Risk factors for kyphosis

  • Old age – elderly people are more likely to develop kyphosis because of osteoporosis.
  • Gender - Available research shows that women are at a higher risk of developing kyphosis than men.
  • Teenage girls are at an increased risk of developing postural kyphosis because of poor posture.
  • Vertebral fractures – these are different from arm or leg fractures as they mostly involve the spinal cord. The spinal cord is protected by the spinal column and any damage to the column can cause injury to the spinal cord. Some of these injuries are known to make the spine bend.
  • Osteoporotic fractures – the spine is composed of small bones known as vertebrae. Weakness or fractures to these bones can make someone develop a hunched posture.
  • Traumatic fracture – spinal fractures can be caused by car accidents or falls from a significant height. People with traumatic fractures to their spinal cords risk developing kyphosis if the fractures are not treated well and promptly.
  • Osteogenesis imperfecta - also known as brittle bones, it is a rare condition which affects the connective tissue. People with this condition have very fragile bones, which can break or fracture very easily, mostly without any cause. Research has revealed that people with such a condition are at a higher risk of developing kyphosis.
  • Myelomeningocele – this is a birth defect which happens during the early stages of fetal development and can cause kyphosis in a child’s back.
  • Marfan syndrome – it is caused by a genetic mutation in the genes which allows collagen cross-linking. Patients with this syndrome have a unique appearance. They are tall, with long legs, arms, and fingers. These patients are mostly associated with scoliosis, which puts them at risk of developing kyphosis.
  • Scheuermann disease – the disease is known to cause back pain, which can lead to long periods of inactivity. If not managed, Scheuermann disease can cause a rounded back, also known as kyphosis.
  • Degenerative disc disease – it’s caused by wear and tear in the spinal cord over a long period of time. Anyone suffering from this disease is also at the risk of developing kyphosis.

All these risk factors can lead to spinal kyphosis. A person affected by one or more of these risk factors have a higher chance of getting kyphosis compared to a person unaffected by any of these risk factors. All the same, the fact that you are not affected by any of the risk factors in no way means that you are safe and can't contract kyphosis.


Normally, the bones of a healthy spinal column (the vertebrae) are stacked one on top each other, like cylinders, with intervertebral discs in between each pair. When the bones in the upper portion of the back begin to become shaped like wedges instead of cylinders, kyphosis occurs. This abnormal curve can be caused by several different problems or a combination of problems. Common kyphosis causes include:

  • Osteoporosis: This is a disorder of the bones that can result in compression fractures of the vertebrae, or of any other bone; the thin and fragile bones are crushed or broken in the incident of a fall, accident or any injury, that can then lead to kyphosis. Osteoporosis most commonly occurs in older adults, especially post-menopausal women. People who have taken corticosteroids in high doses over long periods of time are also at increased risk for osteoporosis.
  • Disk degeneration: The intervertebral discs lie between the individual vertebrae of the spine and act like shock-absorbers. As we age, these discs degenerate, meaning they become dry and shrink. This can cause increased problems with kyphosis.
  • Scheuermann's disease: Scheuermann’s disease is responsible for causing kyphosis among young people. This is a disease that begins in adolescence, typically before puberty. It is also called Scheuermann's Kyphosis. It is more common in males than in females. The kyphosis may continue to worsen as the teen matures. The cause of the disease is unknown.
  • Birth defects: If the spinal column does not properly develop while the fetus is in the womb, the vertebrae may not properly form and kyphosis may result. In some cases, two or more vertebrae join together. Doctors have not yet understood why this condition happens at this stage. However, scientists have discovered that this condition can run in families, and have stated that genetics play a role in such cases.
  • Syndromes: Children sometimes develop kyphosis that is related to certain disorders such as Prader-Willi disease or Marfan Syndrome.
  • Cancer and cancer treatments: The presence of a malignancy in the spine can create weakness and make the vertebrae more susceptible to injury and deformities such as kyphosis. Radiation treatments and chemotherapy also can weaken the bones of the spine and lead to compression fractures.
  • Paget’s disease: this disease disrupts the development of new back bone cells, hence weakening the bones.
  • Muscular dystrophy: a condition which leads to a progressive weakening of the back muscles. It is also said to be genetic.
  • Spinal injuries are also known to cause kyphosis.
  • Arthritis – it can cause inflammation of the joints in the spine. The inflammation can then make the spine to become rigid, creating spinal instability. Therefore, anyone suffering from the arthritis of the spine can develop kyphosis as a result of the spinal instability.

Postural kyphosis is a condition that is not related to any physical deformities. The increased kyphosis in the upper back, in this case, is caused by slouching, carrying heavy bags or leaning back in chairs. Postural kyphosis can make the muscles and ligaments which support the backbone to stretch. This can force the upper back to bend out of its normal position. It is most prevalent in teenagers.


There are several different types of kyphosis. They include:

  • Postural kyphosis: This is the most prevalent kind of kyphosis. Slouching is normally believed to be the primary cause of the condition and young people, as well as the elderly, can develop it. In young people, it is generally a reversible condition that resolves when muscular imbalances are corrected. In older people, the disorder is sometimes known as a "dowager's hump." Approximately one-third of the elderly who have severe postural kyphosis have fractures of the vertebrae.
  • Scheuermann's kyphosis: This disorder causes a more extreme physical deformity and it can also cause pain. It is also known as Scheuermann's disease. This condition can affect various areas of the spine but it most commonly affects the thoracic (upper back to neck) area. This type of kyphosis usually starts in puberty and is more common in boys. Patients with Scheuermann's kyphosis are physically unable to correct their posture. Portions of their spine, especially the thoracic vertebrae, are very stiff and rigid. These areas may be very painful and the pain increases with activity and also with extended periods of sitting or standing. This kyphosis can have a devastating effect on a teenager's life. They may feel uneasy around their friends or isolated and shamed, depending on the severity of the deformity. When comparing Scheuermann's to postural kyphosis, the vertebrae and discs are very different. In postural kyphosis, the structures appear normal. In this condition, the bones are misshapen, irregular and are often herniated. Probably because of the intense amount of muscle effort that is required to sit and stand properly, fatigue is a common symptom. Scheuermann's kyphosis seems to have familial tendencies. Most patients who undergo surgery because of their kyphosis have Scheuermann's disease.
  • Congenital kyphosis: If kyphosis is present at the time of birth it is known as congenital kyphosis. It can occur as the result of problems with the development of the spinal column while a fetus is developing in the uterus (womb) of its mother. The vertebrae can be misshapen, or they can be fused together and this causes the kyphosis to progress further as the child grows. Sometimes surgery is needed very early to help prevent abnormal spinal curvature, and close monitoring is necessary to watch for changes. There are potential risks to the child, so the decision to proceed with the surgery for the kyphosis can be difficult. Sometimes congenital kyphosis is present at birth, but does not appear until the child is older. This happens more frequently with children who have neurological disorders such as cerebral palsy.
  • Nutritional kyphosis: This kyphosis occurs as the result of nutritional deficits, especially in childhood, that affects the bones. One example of nutritional kyphosis is the curving of the spine that results from a deficiency of vitamin D. This can cause rickets which results in soft bones. This not only produces kyphosis of the spine, it also can cause the bones of the limbs to curve under the weight of the child's body.
  • Gibbus deformity: This type of kyphosis often occurs following an infection with tuberculosis. It can happen as a result of the vertebrae collapsing.
  • Post-traumatic kyphosis: As the name implies, post-traumatic kyphosis is a disorder that can be the result of a serious accident or injury, for example, falling from a significant height, a car accident or a horseback accident. The impact of these events can cause dislocations and/or fractures of the spine or the spinal discs. Post-traumatic kyphosis can develop if these conditions are not promptly or properly treated.
Kyphosis definition
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