To better understand the potential causes of kyphosis, it's useful to learn more about the structure of the spine.
The spine
Your spine extends from your skull to your pelvis. It's made up of 24 individual rectangular-shaped bones called vertebrae, which are stacked on top of one another.
The vertebrae are separated by soft pads, or discs, which act as shock absorbers.
The vertebrae are also held together by tough bands of tissue called ligaments. Together with the spinal muscles, the ligaments give the back its strength.
In cases of kyphosis, the middle section of vertebrae, which are known as the thoracic vertebrae, are curved out of position.
There are several reasons why these vertebrae can be affected in this way. They are discussed below.
Bad posture
Poor postural habits in childhood, such as slouching, leaning back in chairs and carrying heavy backpacks and schoolbags, can cause stretching of the ligaments and, in some cases, the muscles that support the vertebrae. This in turn can pull the thoracic vertebrae out of their normal position, resulting in kyphosis.
Kyphosis resulting from bad posture is medically known as postural kyphosis.
Abnormal-shaped vertebrae
Kyphosis can be caused when the vertebrae don't develop in the right way. They take on a wedged, triangular shape rather than a rectangular, box-like shape. This leads to the vertebrae being out of position. It's known medically as Scheuermann’s kyphosis.
The ligaments in people affected by Scheuermann's kyphosis also appear to be thicker than normal. This may contribute further to the condition.
It's unclear exactly what disrupts the normal formation of the spine. One idea is that the blood supply to the vertebrae becomes disrupted, affecting the growth of the vertebrae.
There also appears to be genetic factors associated with Scheuermann's kyphosis as the condition runs in families.
Congenital kyphosis
Congenital kyphosis is caused when something disrupts the normal development of the spine before birth. In many cases of congenital kyphosis, two or more of the vertebrae fuse together.
It's often unclear why certain children are affected in this way. But some cases of congenital kyphosis run in families, so it seems that genetics also play a role in this type of kyphosis.
Conditions that cause kyphosis
Conditions that can cause kyphosis include:
- osteoporosis
- spondylosis – a medical term used to describe the general ‘wear and tear’ that occurs in the bones, discs and ligaments of the spine as a person gets older
- spina bifida – a birth condition where the spine hasn't formed properly
- Paget's disease – a condition in which the development of new bone cells are disrupted, leading to the weakening of the bones
- neurofibromatosis – a genetic disorder that affects the nervous system
- muscular dystrophy – a genetic condition that causes progressive weakening of the muscles
- tuberculosis – a bacterial infection that mainly affects the lungs but can sometimes spread
- cancer that develops inside the spine or spreads to the spine from another part of the body
Kyphosis can also develop as a result of an injury to the spine.
