Dorsal kyphosis is a technical term for a very common phenomenon, which is that of a rounded upper back posture. The slang term for this phenomenon is a hunchback. Weak or overstretched muscles in the upper thoracic area account for many cases of dorsal kyphosis.
Especially in the age of technology, where automation spares us from quite a bit of physical work compared to generations past, our muscles, including those in the upper back, may miss out on conditioning that could otherwise result from our daily activities.
Weak or overstretched upper back muscles may contribute to a dorsal kyphosis condition.
When they are well-toned, upper back muscles preserve good alignment in the thoracic spine. But when they are weak, they lose their power to keep the vertebrae in the mid and upper back "in check." The result may be a backward migration of those bones, aka, dorsal kyphosis.
In fact, the amount of muscle mass in the paraspinals, which are the long back muscles that extend from your neck all the way down to your low back, may be responsible for the presence or development of dorsal kyphosis. A 2014 study published in the journal BMC Musculoskeletal Disorders found that, in older men, at least, not being obese, as well as having small paraspinal muscles was associated with a greater degree of kyphosis, especially when compared with men with more paraspinal mass.1
What Is Kyphosis?
When you view an X-ray or diagram of the body from the side, you can see that the spine curves in alternating directions. In the neck, the curve sweeps towards the front of the body. Just below, the thoracic curves go towards the back. Like the cervical (neck) curve, the low back curves towards the front.
A kyphotic curve, as it's often called, occurs naturally in your thoracic spine as well as your sacrum, but it is not natural in the cervical (neck) and lumbar (low back) regions. The neck and low back curves go in a forward direction when you view the body from the side. These called lordotic curves, or lordosis.
This is not to say that kyphosis is always normal in the upper and/or mid-back area. Kyphosis can be excessive, and that's where the problems begin.
Also, the sacrum is one bone that is fused together from five. This means the degree of its curve is not affected by things like posture habits or the condition of your muscles. And so the discussion of excessive dorsal kyphosis to a great extent only applies to your thoracic spine — i.e. your mid to upper back area.
What Curve Measurement Is Normal or Excessive?
Historically, the thoracic kyphotic curve has been measured using a calculation called the Cobb Angle. (The Cobb angle is also used to determine the degree of scoliosis curves.) More recently, however, researchers have been developing other methods of measurements.2
At any rate, if your thoracic kyphosis measures between 20 and 40 degrees, it's considered normal. Above 45 degrees, your doctor may diagnose you with excessive kyphosis, or hyperkyphosis, which are two terms that basically mean the same thing. Other names include Gibbous deformity and Dowager's Hump.
Hyperkyphosis affects many different types of people (often for different reasons) with senior citizens3, adolescents whose skeletons haven't matured yet, office workers, people with scoliosis topping the list.
A number of conditions can lead to excessive kyphosis, including muscle weakness, degenerative disc disease, vertebral fractures, genetic conditions, or simply advancing age. Excessive kyphosis is associated with spinal fractures, according to a 2017 study published in Osteoporosis International.4
No matter what the cause is, getting hyperkyphosis diagnosed and treated early may help you avoid the negative impact it can have on your quality of life. Hyperkyphosis may cause headaches, shoulder problems, reduced lung functioning, neck pain and/or upper or mid-back pain.