What condition is characterized by a sideways deviation of the spine, forming either an S or a C?

Scoliosis is a condition that specifically involves an abnormal curvature of the spine, resulting in a sideways deviation which can resemble either an "S" or a "C" shape when viewed from the back. This deviation can occur in the thoracic or lumbar regions of the spine and may lead to discomfort or health issues if not addressed. Scoliosis can develop in childhood or adolescence, but it may also occur in adults due to degenerative changes or other factors.

In contrast, kyphosis refers to an exaggerated forward rounding of the back, typically affecting the thoracic spine, creating a hunched appearance rather than sideways deviation. Lordosis describes an increased curvature of the lumbar spine, often resulting in an inward curve, and is not characterized by lateral deviation. Osteoporosis is a condition that leads to weakened bones and increased fracture risk but does not specifically pertain to spinal curvature. Therefore, scoliosis is rightly identified as the condition characterized by the distinctive "S" or "C" shape of the spine.