The pelvis makes a significant contribution to the functional capacity of the musculoskeletal system for the following reasons:

• The superior surface of the body of the sacrum supports the vertebral column and the sacroiliac joints couple to the lower extremities. Consequently, alterations in normal sacral mechanics can have a significant effect on both body support and locomotion.
• The pelvis is important in the respiratory circulatory model because of it's relationship to the pelvic diaphragm. Dysfunction of the bony pelvis can alter the functional capacity of the muscles of the pelvic diaphragm in a similar fashion to thoracic spine and rib dysfunction on the thoracoabdominal diaphragm.
• The sacral component of the pelvis is of importance within the craniosacral system. The sacrum has inherent mobility between the two innominates as part of craniosacral rhythm. Alterated mechanical function of the pelvic girdle can negatively influence the craniosacral mechanism, and alterated craniosacral mechanics can influence the biomechanical function of the osseous pelvis.

Structural diagnosis is performed with the patient standing, sitting, prone, and/or supine. The examiner is looking for combinations of asymmetry, range of motion, and tissue texture abnormalities that lead to the diagnosis of pelvic girdle dysfunction at the:

• Pubic symphysis -- dysfunction between the two pubic bones
• Sacroiliac joints -- dysfunction between the two inniminates
• Iliosacral joints -- dysfunction between each innominate and the sacrum