The variation in joint configuration results in some sacroiliac joints being inherently weaker or more prone to misalignment.Certain biomechanical or muscle length imbalances may ultimately predispose a person to sacroiliac dysfunction and pain. Likely, this is a result of altered gait patterns and repetitive stress to the SI joint and related structures. These conditions exist in persons with leg-length inequality, scoliosis, a history of polio, poor-quality footwear, and hip osteoarthritis.There is also a notable incidence of lumbar spinal fusion patients that present with sacroiliac pain and hypermobility, potentially due to the adjacent lumbar joints being fixed and unable to move. Clinical studies have found up to 75% of post-lumbar fusion patients develop SI joint degeneration within five years of surgery. Hypomobility
Pathological hypomobility (too little movement) of the sacroiliac joint is an intra-articular disorder in which the joint locks due to wearing down with age or degenerative joint disease.Hypomobility of this kind can also occur with an inflammatory disease such as ankylosing spondylitis, rheumatoid arthritis, or an infection. Pathophysiology
The sacroiliac joint is a true diarthrodial joint that joins the sacrum to the pelvis. The sacrum connects on the right and left sides to the ilia (pelvic bones) to form the sacroiliac joints. The pelvic girdle is made up of two innominate bones (the iliac bones) and the sacrum. The innominate bones join in the front of the pelvis to form the pubic symphysis, and at back of the sacrum to form the sacroiliac (SI) joints.
Any of these muscles can be involved or spasm with a painful and dysfunctional sacroiliac joint. The SI joint is a pain-sensitive structure richly innervated by a combination of unmyelinated free nerve endings and the posterior primary rami of spinal segments L2-S3. The wide possibility of innervation may explain why pain originating from the joint can manifest in so many various ways, with different and unique referral patterns (see "referred pain") for individual patients. Patients with sacroiliac joint dysfunction can also develop tightness and dysfunction in the hamstring, quadriceps, iliotibial tract (see "iliotibial band syndrome") and hip flexors, including the psoas muscle. Individuals with severe and long-standing sacroiliac joint dysfunction can develop muscle deconditioning and atrophy throughout the body due to limitation of activities and exercise that bring about pain in the low back. Diagnosis
Perhaps the biggest reason for misdiagnosis or lack of diagnosis of sacroiliac joint dysfunction is based on the inability of common radiological imaging to discern the disorder. Diagnostic testing, such as X-ray, CT scan, or MRI, do not usually reveal abnormalities; therefore, they cannot reliably be used for diagnosis of sacroiliac joint dysfunction. There is a new imaging test SPECT/CT which can sometimes detect sacroiliac joint dysfunction. There is also a lack of evidence that sacroiliac joint mobility maneuvers (Gillet, Standing flexion test, and Seated Flexion test) detect motion abnormalities. Given the inherent technical limitations of the visible and palpable signs from these sacroiliac joint mobility maneuvers another broad category of clinical signs have been described called provocative maneuvers.