When viewed from the front, the healthy spine is straight. Viewed from the side, the spine has four distinct curves. These curves are described as being either kyphotic or lordotic.
A kyphotic curve is a convex curve in the spine (i.e., convexity towards the back of the spine). The curves in the thoracic and sacral spine are kyphotic.
A lordotic curve is concave (i.e., concavity towards the back of the spine) and is found in the cervical and lumbar levels of the spine.