Sacroiliac joint dysfunction generally refers to pain in the sacroiliac joint region that is caused by abnormal motion in the sacroiliac joint, either too much motion or too little motion. Signs and symptoms
Common symptoms include lower back pain, buttocks pain, sciatic leg pain, groin pain, hip pain (for explanation of leg, groin, and hip pain, see referred pain), urinary frequency, and "transient numbness, prickling, or tingling." Pain can range from dull aching to sharp and stabbing and increases with physical activity. Symptoms also worsen with prolonged or sustained positions (i.e., sitting, standing, lying). Bending forward, stair climbing, hill climbing, and rising from a seated position can also provoke pain. Pain can increase during menstruation in women. People with severe and disabling sacroiliac joint dysfunction can develop insomnia and depression. Sacral torsion that is untreated over a long period of time can cause severe Achilles tendinosis. Causes
Hypermobility
Sacroiliac joint dysfunction is an outcome of either extra-articular dysfunction or from intraarticular dysfunction. SI joint dysfunction is sometimes referred to as "sacroiliac joint instability" or "sacroiliac joint insufficiency"  due to the support the once strong and taut ligaments can no longer sustain. When the joint is hypermobile or loose, it is classified as an extra-articular dysfunction because abnormal joint movement and alignment is a consequence of weakened, injured, or sprained ligaments, while the joint itself is structurally normal and healthy. The sacroiliac joint itself often will not show degenerative changes, such as arthritis, until many years of the dysfunction being allowed to continue.
Misdiagnosis
In the early 1900s, dysfunction of the sacroiliac joint was a common diagnosis associated with low back and sciatic nerve pain. However, research by Danforth and Wilson in 1925 concluded that the sacroiliac joint could not cause sciatic nerve pain because the joint does not have a canal in which the nerves can be entrapped against the joint. The biomechanical relationship between the sacroiliac joint, the piriformis muscle (see "piriformis syndrome"), and the sciatic nerve had not yet been discovered.In 1934, the work of Mixter and Barr shifted all emphasis in research and treatment from the sacroiliac to the herniated intervertebral disc, namely lumbar discs. Medical focus on herniated discs was further forwarded by the invention of the MRI in 1977. Over-diagnosis and attention on herniated discs has led to the SI joint becoming an underappreciated pain generator in an estimated 15% to 25% of patients with axial low back pain.The ligaments in the sacroiliac are among the strongest in the body and are not suspected by many clinicians to be susceptible to spraining or tearing. Skepticism of the existence of sacroiliac joint dysfunction within the medical community is furthered by the debate on how little or much the sacroiliac joint moves. A discrepancy as large as 2-17 degrees has been reported in clinical findings. Treatment
Treatment is often dependent on the duration and severity of the pain and dysfunction.