Overview
Sagittal imbalance implies a patient is unable to maintain a normal weight-bearing line between their head and their pelvis when viewed from the side. In basic terms, they cannot stand up straight. Depending on the degree of the problem, patients may be able to compensate by flexing their knees and/or hips, or strengthening their posture muscles. In general, the more the person leans forward, the more gravity will cause the body to lean forward further.
Normal Anatomy All spines have kyphosis (forward bend), but it is typically limited to the thoracic spine. The body balances the thoracic kyphosis with lordosis (backward bend) in the cervical and lumbar spines. The body usually has approximately equal degrees of lumbar lordosis and thoracic kyphosis, although this can vary with age, degrees of arthritis, and various disease processes. The body’s normal weight-bearing line extends from the skull (C1) through the first vertebra of each section of the spine (T1, L1, S1). Physicians call this line the “C7 plumb line”. If there is a loss of lumbar lordosis and/or increase in thoracic kyphosis, this weight-bearing line can move in front of the spine and hips.
