Kyphosis can be a confusing medical term because it's also used as a description of a spinal curve. In fact, even people with healthy spines have a kyphotic curve, as you'll learn in the Anatomy of Kyphosis article. Your mid-back region (thoracic spine) is supposed to curve outwards, or have a kyphotic curve. However, too much kyphosis in the thoracic spine is abnormal, and it's called hyperkyphosis, problematic kyphosis, or abnormal kyphosis. (In this article series, we'll call an extreme kyphotic curve abnormal kyphosis.)

Also, if your neck (cervical spine) or low back (lumbar spine) develop a kyphotic curve of any degree, that's considered abnormal. Your cervical spine and lumbar spine are supposed to have a lordotic curve; that's an inward curve.

Some people may call abnormal kyphosis just plain slouching, but it is more than that. It changes the way your spine works, and it can be very painful.

There are two types of abnormal kyphosis: structural and postural.

• Structural kyphosis involves an actual defect in part of the spine. For example, Scheuermann's disease, a type of structural kyphosis that affects adolescents, occurs when the front sections of the vertebrae don't grow as fast as the back sections. This results in wedge-shaped vertebrae instead of more rectangular ones that line up well.
• Postural kyphosis is related to poor posture. Constant slouching can cause the spine to become more curved.