Sacralrange

Sacralrange is a term used in biomechanics and physical therapy to denote the mobility range of the sacrum within the pelvis, focusing on how the sacral base moves relative to the ilia during dynamic tasks. It is not a universally standardized metric; definitions and measurement approaches vary among researchers. The term is a neologism combining sacrum and range of motion, and is sometimes used to describe movements such as nutation and counternutation of the sacral base, as well as translational shifts in the sagittal or transverse planes.

Measurement methods include dynamic imaging with fluoroscopy or cine radiography, three-dimensional motion capture with pelvic markers, and, in some protocols, manual assessment under standardized loading. Reported metrics may refer to degrees of nutation/counternutation, or to millimeters of sacral translation relative to the pelvis, under specified tasks like bending, walking, or load transfer. There are no widely accepted normative values; estimates vary with pelvic tilt, spinal posture, age, sex, and pregnancy status.

Potential applications include clinical assessment of sacroiliac joint stability, tracking mobility changes during rehabilitation, and research on how sacral mobility relates to low back pain, gait, or obstetric conditions. Limitations include high inter- and intra-individual variability, sensitivity to posture, measurement error, and the lack of standardized protocols. Further research is needed to establish reliable protocols and normative data.

See also: sacrum, sacroiliac joint, nutation, counternutation, pelvic tilt. References: literature on sacroiliac mobility and sacral kinematics.