Pelvic, Hip, Groin and Back Pain
Both the pubic symphysis and sacroiliac joints are held together by strong fibrous and ligamentous attachments. The pubic symphysis is actually a disc. It is a fibrocartilaginous disc that, like any other disc in the body, can be disrupted. The pubic symphysis is also strengthened by the pubic arcuate ligament and superior pubic ligament. The sacroiliac joint also has extremely strong ligamentous attachments. These consist of the iliolumbar, sacrotuberus, sacrospinus, and anterior and posterior sacroiliac ligaments, which resist downward and forward forces from the lumbar spine and upward forces from the hip joint.
The sacroiliac joint is normally very stable with a limited amount of movement because of this tight ligamentous support, but laxity can easily develop if the ligamentous support is injured.
Injuries to these ligaments are a common cause of sciatica and chronic low back pain. The sacroiliac joint is a true arthrodial (gliding) joint with hyaline articular cartilage, synovial membrane, and a capsule. This has been forgotten by modern orthopedics, who still believe the sacroiliac joint is rather immobile and almost incapable of being injured.
Because the pubic symphysis and the sacroiliac joint are the only two joints connecting the two halves of the pelvis, an injury to one can affect the other. Thus, anyone sustaining injury to a sacroiliac joint should also have the pubic symphysis examined. Many athletes with chronic low back pain could have been easily treated if someone would have also examined the pubic symphysis, instead of just examining the lower back.
The rather immobile sacroiliac joint is located between a fairly mobile lumbar spine and a very mobile hip joint. The function of the sacroiliac joint is related to both areas. The joint acts like a buffer zone that enables the forces to be transmitted from the femur to the ilium to the lower back, as well as from the lower back to the ilium to the femur. The absorption of forces in the sacroiliac joint reduces the stress on the pelvis. It can easily be seen how the sacroiliac ligaments are injured because they are, in essence, the primary shock absorbers between the hip and lower back vertebrae. Any tackle, body smash, knee contusion, or fall that transmits forces from the back to the lower extremity or vice versa must travel directly through the sacroiliac ligaments.
The often-overlooked pubic symphysis plays a role very similar to that of the sacroiliac joint by enhancing overall pelvic mobility. It also is the site of attachment of the powerful adductor muscles, which move the leg inward, and the abdominal muscles whose strength helps keep force off of the lower back and discs.