Mend Physical Therapy Blog and Injury Information

Why Your SI Joint Is An Unlikely Contributor To Your Current Symptoms

November 6, 2019


Healthcare demonstrates significant swings of the pendulum in examination and treatment trends. Thankfully the medical evidence helps balance these swings allowing us to come to a more appropriate balance in clinical practice. Unfortunately, unchecked bias in a clinician, such as confirmation bias, can lead to missed diagnoses and inappropriate treatments. In Physical Therapy, this can be found among providers who search for clinical support of the diagnosis and treatment of SI dysfunction (sacroiliac) but refuse the clinical evidence which refutes those thoughts and beliefs. The selective biased utilization of the evidence leads to over diagnosis and over treatment of this uncommon problem.

The sacroiliac joint is the connection between our large pelvic bones (innominates) and our triangular sacral bone. This joint is built for stability and weight bearing benefiting from strong bone contact, ligamentous support, and large muscle connections further enhancing its stability. For example, authors have described only 4 degrees or 1.5 mm of motion under 225 lbs of force placed on the SI joint. As we age past 30 years old the smooth cartilages surfaces of the innominate become bony ridges further stabilizing the joint. These changes lead to a progressive loss of joint movement as we age with researchers finding 1-2 mm and 0-1 mm of motion in the average 50 and 70 year old, respectively. As expected the already small incidence of SI joint pain and dysfunction significantly reduces as we age and its’ limited motion questions the ability of providers to examine its’ movement.

Along with death and taxes, low back pain remains one of the certainties of life with over 90% of patients reporting symptoms during their lifetime. As we have written in previous blogs the vast majority of cases are benign in nature and resolve rapidly with Physical Therapy treatments. Within the chronic low back pain population, only about 13% of patients will respond to SI joint injections, indicating this joint may be indicated as the pain generator. Despite this low incidence biased clinicians often find a significantly higher incidence in their practice and treat accordingly.

Early examination of the SI joint was founded on the location of bony landmarks of the pelvis and assumptions of static position based on these landmarks. This type of examination is layered with potential errors including inability to reach these landmarks due to patient skin and tissue and a lack of anatomical symmetry of landmarks. For example, asymmetry of the landmarks is the norm in the pelvis not the exception and a larger or smaller landmark will make the opposing landmark appear different in location. Is it high, low, rotated or just naturally a different size?

Our SI testing evolved beyond static palpation of anatomical landmarks into the assessment of movement of these joints. Errors can already be expected with this exam based on the aforementioned paragraph and our limited ability to actually find these landmarks with certainty. As expected, SI testing involving movement at this joint has also been called in question in the literature.  Previous studies have found abnormal or asymmetrical movement in both asymptomatic and symptomatic patients, as well as, on the involved or uninvolved sides of the pelvis.  These asymmetries contribute to the poor diagnostic utility of these tests with significant false positive and false negative rates.  More recent research has shown asymmetries in these tests are secondary to weakness and coordination impairments instead of changes in SI joint mobility. This highlights the importance of core strengthening exercises within this population group.

The poor reliability and validity of the clinical examination items reported above have led to a new strategy in diagnosing painful SI joints.  Experts agree a cluster of 3-4 provocative tests should be administered to improve the diagnostic utility of our clinical examination.  Ruling out the lumbar spine, the most probably reason for low back pain, prior to administering these clusters of tests also has been shown to improve our accuracy in determining a painful SI joint. Once the joint is identified as a pain generator treatment involving manual therapy and exercise has been shown to reduce pain and disability ini this patient population.

In conclusion, the SI joint is a joint built for stability and in the absence of trauma or certain conditions including pregnancy is an uncommon source of pain or instability.  Further the inherent stability of the joint makes it an unlikely contributor to a patient’s pain in an adjacent areas such as the lumbar spine or hip.  Clinical examination of this area should include a thorough history, lumbar exam, and SI pain provocation cluster of tests to confirm a suspected diagnosis of SI dysfunction.  Research has shown those affected with SI pain respond well to manipulation and core stabilization exercise. 

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