Sacroiliac joint pain
What is Sacroiliac (SI) joint pain? SI injuries have gained a lot of attention in the last ten years as an underappreciated cause of back pain with some studies indicating it is responsible for 15% to 40% of low back pain. The increased attention is due to the increasing knowledge of the SI joints intimate role in pelvic stability. I hope more physicians consider SI joint pain in their differential after reading this article.
Work injuries involving the SI joint are due to instability of the SI joint. Experts believe that SI joint pain is a component of a larger problem of pelvic instability(1). Pelvic instability has traditionally been underappreciated as a cause of low back pain, buttock pain, groin pain, and leg pain. Physical therapists and doctors of osteopathic medicine have been teaching these concepts for years but only relatively recently has this dissemination of knowledge trended towards mainstream thinking among medical doctors.
The SI joint complex (the SI joint and its associated ligaments) is the major support structure of the pelvic ring and is the strongest ligament complex in the body. The complex consists of interosseous sacroiliac ligaments, iliolumbar ligaments, posterior sacroiliac ligaments, and the sacrotuberous and sacrospinous ligaments. The SI joints are two of the three joints involved in the stability of the pelvic ring. The pelvic ring is the meeting place of the force vectors from the upper body and the lower extremities. The third joint in the pelvic ring is the pubis symphysis. Pelvic instability causes pelvic rotation which can also cause twisting of the pubis symphysis. Coupling this with its anterior location appears to provide an explanation as to why patients with SI joint instability can also experience anterior groin pain. Anecdotal evidence for this is seen when patients undergo a successful SI joint intra-articular injection relieving all of their posterior back, buttock, and leg symptoms but the patient still has groin pain. Groin pain is almost never eliminated by SI joint injections unless pelvic symmetry is corrected.
If the SI joints are unstable, it can lead to significant pain and discomfort over the SI joints as well as numerous referred areas. If an individual affected by SI joint pain has pain only over his or her SI joint, he/she should be considered lucky. Most often SI joint instability causes unnatural strain on the entire low back and pelvic region causing a sometimes confusing clinical picture.