Along with the two sacroiliac joints, the symphysis pubis forms part of a triad of joints (with the two sacroiliac joints) which interconnect to provide stability and motion to the pelvis.
Symphysis Pubis Ligaments
Like the ligamentous region of the sacroiliac joint, symphysis pubis is a syndesmosis and is composed of three ligaments:
- A superior pubic ligament connects the superior part of the joint
- An inferior (arcuate) public ligament connects the inferior part of the joint
- An interpubic disc separates and connects the opposing surfaces much like the interosseous ligament in the sacroiliac joint
Range of Motion
In a study of 4 cadavers and 15 healthy volunteers, Walheim et al.  found movements of the symphysis pubis were small. Vertical translations averaged around 2.5 mm, while transverse and sagittal translations were less than 1mm. Rotation in the frontal and sagittal planes were also less than 1 mm with rotations up to 3 degrees. No significant differences were noted between the males and females except for the pregnant women, which were more mobile.
Symphysis Pubis Syndrome
Classical findings of pubic symphysis syndrome include pubic gaping, pain associated with walking, tenderness, crepitus, excessive motion upon pressure, and external rotation of the acetabula [2, 3 ].
Callahan  further stated that “Even 3 to 5 cm separations cannot be considered as true ruptures in the absence of clinical symptoms. Generally, however, separations of 1.0 cm or over are considered to be symptom producing.” He promotes diagnosis of pubic separation through signs and symptoms rather than the use of x-rays, claiming that separation of the pubis is rare, occurring in about 1 in 2,000 women during, or after, delivery. In those cases, he says that strapping the pelvis (e.g. with a sacroiliac belt) is usually sufficient treatment.
However, Chamberlain  developed a series of 5 x-ray procedures that use variations in height of the two sides of the symphysis pubis as a diagnosis of “sacroiliac slip”. Some authors currently regard this technique as the only x-ray method to accurately measure sacroiliac dysfunction.
Using two of Chamberlain’s procedures, the single-leg stance compared to double leg stance, but with a more controlled study population, Garras  found translation at the symphysis pubis to average 1.4 mm for men, 1.6 mm for nulliparous women, and 3.1 mm for multiparous women.
The symphysis pubis joint and sacroiliac joints are interdependent and function as a unit  . Berg et al.  found that “Symphysiolysis was significantly more common among women with dysfunction of the sacroiliac joints than among pregnant women without backache, supporting earlier suggestions that hormonal effects are an important cause of instability in the pelvis.”
Bellamy  stated that “The most reliable clinical sign of instability of disruption of the SI joint is that of disruption of the pubic symphysis.”
Vleeming et al.  stated that “hypermobility of the symphysis is accompanied by hypermobility in the sacroiliac joint.”
- Walheim, G., S. Olerud, and T. Ribbe, Mobility of the pubic symphysis. Measurements by an electromechanical method. Acta Orthop Scand, 1984. 55(2): p. 203-8.
- Callahan, J.T., Separation of the symphysis pubis. Am J Obstet Gynecol, 1953. 66(2): p. 281-93.
- Taylor, R.N. and R.D. Sonson, Separation of the pubic symphysis. An underrecognized peripartum complication. J Reprod Med, 1986. 31(3): p. 203-6.
- Chamberlain, W.E., The Symphysis Pubis in the Roentgen Examination of the Sacroiliac Joint. American Journal of Roentgenology and Radium Therapy, 1930. 24(6): p. 621-625.
- Garras, D.N., J.T. Carothers, and S.A. Olson, Single-leg-stance (flamingo) radiographs to assess pelvic instability: how much motion is normal? J Bone Joint Surg Am, 2008. 90(10): p. 2114-8.
- Levangie, P. and C. Norkin, Joint Structure and Function. A Comprehensive Analysis. 2005, Philadelphia, PA: F.A. Davis Company.
- Vleeming, A., et al., An integrated therapy for peripartum pelvic instability: a study of the biomechanical effects of pelvic belts. American journal of obstetrics and gynecology, 1992. 166(4): p. 1243-7.
- Berg, G., et al., Low back pain during pregnancy. Obstet Gynecol, 1988. 71(1): p. 71-5.
- Bellamy, N., W. Park, and P. Rooney, What Do We Know About the Sacroiliac Joint. Seminars in Arthritus and Rheumatism, 1983. 12(3).
- Vleeming, A., et al., Relation between form and function in the sacroiliac joint. Part II: Biomechanical aspects. Spine, 1990. 15(2): p. 133-6.