As an important part of human anatomy, the spine helps us move, maintain balance, and stand upright. It has three main natural and healthy curves that give the spine a soft ‘S’ shape when viewed from the side. There are a number of spinal conditions that can develop and involve a loss of one or more of these healthy curvatures: ‘kyphosis’ is one such condition.
While scoliosis is defined as an abnormal sideways curvature of the spine, kyphosis is more of a forward-rounding curvature of the upper back, giving it somewhat of a rounded or hunched appearance. While the two conditions share some similarities and you can have them both at the same time, they also have important differences worth noting.
Before we move onto the specifics of kyphosis, scoliosis, and the connection between the two, let’s spend a little time exploring some basic spinal anatomy, including the nature of the spine’s healthy curvatures.
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Once you understand just how and why the spine is curved, it’s far clearer how conditions that impact these curvatures affect the spine in its entirety, and by extension, the rest of the body.
The spine has three main sections: cervical spine (upper back and neck), thoracic spine (middle back), lumbar spine (lower back).
Each of these sections has a characteristic curvature that goes along with it. The spine’s ‘C’-shaped curves occupy the cervical and lumbar spine, and these are referred to as ‘lordosis’, and the reverse ‘C’-shaped curve of the thoracic spine is referred to as ‘kyphosis’.
In the medical world, the body is divided into sections, or planes, and these planes help us describe and understand where conditions are occurring and areas of the body they are affecting.
The coronal plane divides the front and back halves of the body, and the sagittal plane separates the left and right sides of the body (this will be important later).
The spine’s curvatures facilitate some pretty crucial functions: balance, standing upright, and giving the spine its strength and flexibility.
If one or more of these curves becomes over- or under-pronounced, it can lead to a host of problems and an inability to stand upright with good posture.
First, let’s address what kyphosis is, and then we will bring scoliosis into the discussion.
An average healthy spine should have a natural kyphosis (front-to-back curve) of anywhere between 20 and 45 degrees.
When a condition affecting the spine develops, the curvature can move into an area beyond this normal range.
The terms ‘kyphosis’ and ‘hyperkyphosis’ refer to excessive curvatures of the thoracic spine that lead to an unnaturally-rounded upper back. Conversely, ‘lordosis’ and ‘hyperlordosis’ refers to excessive inward curvatures, mainly affecting the lower back.
While more common in adolescents, kyphosis can affect people of all ages and vary in severity. Generally speaking, the larger the curve, the more severe the condition is.
Smaller curves can cause some mild back pain or no noticeable symptoms at all, while larger curves can significantly impact the spine and result in a noticeable arch to the upper back.
There are different forms of kyphosis, with three being the most common: postural, Scheuermann’s, and congenital.
The most common type, postural kyphosis typically appears during adolescence, a time of rapid bone growth and development.
It’s mainly noticed as poor posture and/or slouching, but is not associated with structural disorders of the spine.
The upper back’s curvature, caused by kyphosis, is typically rounded and smooth, and when a patient is told to stand up straight, it is temporarily corrected.
This form of kyphosis is rarely painful, and as it is not structural, it won’t progress and doesn’t commonly lead to problems developing later in life.
Scheuermann’s kyphosis also commonly appears during the teenage years, but this form impacts the spine on a structural level, as does scoliosis.
Scheuermann’s kyphosis can develop during adolescence, but progress well into adulthood, just as most cases of adult idiopathic scoliosis are extensions of adolescent idiopathic scoliosis. In these types of cases, both conditions can be exacerbated by degenerative changes to the spine that accompany aging.
Caused by a structural abnormality within the spine, X-ray images of people with Scheuermann’s kyphosis show several of the spine’s vertebrae are misshapen.
If you picture the vertebrae of a healthy spine, they are rectangular in shape, stacked on top of one another, separated by intervertebral discs. If you imagine that several of those bones are triangular in shape, instead of rectangular, this irregularity causes the bones of the spine to wedge together.
As they wedge together, they are pushed towards the front of the spine, and this results in less space for the discs and an over-pronounced forward curvature of the cervical spine.
The curvature that develops is angular, sharp, and rigid, which is why patients with this type can’t simply ‘stand up straight’ to correct it, as they can with a lesser postural kyphosis.
Congenital kyphosis develops in utero and is present at birth. Sometimes, the vertebrae of the spine don’t form properly, or several are fused together into one solid bone.
Patients with this form of kyphosis tend to get worse with age, which is why surgical treatment is sometimes given at a young age to try and stop the curvature from getting worse.
Often, these patients also have other birth defects present.
Now that we have a solid understanding of what kyphosis is and its main types, let’s keep the condition’s characteristics in mind as we bring scoliosis into the discussion.
Further Reading: Kyphoscoliosis: What Is It, Symptoms, Diagnosis, & Treatment
The basics of scoliosis include that it is an abnormal sideways curvature of the spine that includes rotation.
It’s main form accounts for 80 percent of known diagnosed cases: adolescent idiopathic scoliosis (AIS). The other 20 percent have clear known causes such as neuromuscular, congenital, degenerative, and traumatic.
At the time of diagnosis, X-ray images are taken and a measurement known as the ‘Cobb angle’ is taken; this measurement tells us how far out of a normal and healthy alignment the scoliotic spine bends and twists.
The higher the Cobb angle, the more severe the condition is, classifying it as mild, moderate, or severe.
Scoliosis can develop anywhere along the spine and at any age.
Now that we understand the different types of kyphosis and the basics of scoliosis, let’s see how the two connect.
Obviously, scoliosis and kyphosis are both disorders that affect the spine, and they express themselves in the form of abnormal spinal curvatures, but they are different conditions with important distinctions.
Scoliotic curves bend to the side, often taking the form of a letter ‘S’ or ‘C’, whereas kyphotic curves bend forward and result in a rounding of the back, giving the appearance of heavy slouching.
As they are separate conditions with their own characteristics and etiologies, it’s more accurate to say that scoliosis and kyphosis can occur together, rather than attributing the onset of one to another.
Scoliosis refers to abnormal curvatures in the spine’s coronal plane (front to back), while kyphosis involves curves in the sagittal plane (side to side). Now, if a patient were to present with an abnormal curvature that engaged both planes, this is referred to as ‘kyphoscoliosis’, aka ‘scoliosis with a kyphosis’.
As kyphotic curves tend to be more rigid, they are less moveable once they form and skeletal maturity has been reached, unlike scoliotic curves that can progress quickly. Although with a lack of treatment and in severe forms, kyphotic curves are also known to get worse over time.
Just as the initial cause behind the malformed vertebrae in kyphosis is not clearly understood, neither is the etiology of adolescent idiopathic scoliosis.
The general consensus is that both main forms of these conditions are considered ‘idiopathic’, meaning their onset cannot be clearly tied to one single known source, and they are instead considered to be ‘multifactorial’.
So while kyphosis and scoliosis are linked as spinal conditions that produce abnormal curvatures of the spine, they are separate conditions that when expressed together form a combined condition: kyphoscoliosis.
As such an important part of human anatomy, it’s not surprising that there are several conditions that can develop and affect the spine, such as scoliosis and kyphosis.
As the spine’s form and function is facilitated by its natural and healthy curves, when one or more of those curves are lost, the effects can be felt throughout the spine and the rest of the body.
Defined as an abnormal sideways curvature of the spine of more than 10 degrees that includes rotation, scoliosis can range as mild, moderate, or severe.
Scoliosis involves a curvature in the spine’s coronal plane; kyphosis, or hyperkyphosis, refers to an over-pronounced inward curvature that gives the upper back an overly-rounded appearance.
When the two conditions occur together, the combined condition is known as ‘kyphoscoliosis’, and this involves a curvature that occupies both the coronal and sagittal plane.
Perhaps, if we understood more of the governing etiologies of the two conditions, we could more clearly understand the link between the two, but for now, it seems the connection is more correlative than causative.
Here at the Scoliosis Reduction Center, we have treated multiple forms of the condition, kyphoscoliosis included.