Hypokyphosis is defined as having a sagittal curve magnitude in the range of:

Hypokyphosis refers to a reduced or flattened curvature of the thoracic spine in the sagittal plane. In healthy individuals, the thoracic spine exhibits a natural kyphotic curve, generally ranging from about 20 to 40 degrees. When considering hypokyphosis, the definition typically indicates that a person has a curve magnitude at the lower end of this spectrum or even less, which corresponds to minimal or absent curvature.

The range of 0-20 degrees accurately captures this definition, as it encompasses both the absence of a kyphotic curve and a significantly reduced curve, fitting the diagnostic criteria for hypokyphosis. This understanding highlights the importance of the sagittal plane alignment in assessing spinal conditions, as an optimal spinal curvature plays a crucial role in biomechanics and overall function. Thus, the choice that correlates with hypokyphosis accurately reflects the clinical understanding of reduced thoracic curvature.