The examiner provides either a quick thrust or steadily increasing pressure through the line of the femur. The pelvis is stabilized at the sacrum or at the opposite ASIS with the hand of the examinerCautious interpretation is warranted because there are no biomechanical studies showing that the Thigh Thrust test isolates forces in the SIJ when performed at 90 degrees and due to intra-individual variation in body type, hip flexibility, general flexibility of the trunk and pelvis. In all the tests, pain along the typical area raises suspicion for sacroiliac joint dysfunction. However no single test is very reliable in the diagnosis of sacroiliac joint dysfunction. It is important to remember true neurogenic weakness, numbness, or loss of reflex should alert the clinician to consider nerve root pathology.The current "gold standard" for diagnosis of sacroiliac joint dysfunction emanating within the joint is sacroiliac joint injection confirmed under fluoroscopy or CT-guidance using a local anesthetic solution. The diagnosis is confirmed when the patient reports a significant change in relief from pain and the diagnostic injection is performed on 2 separate visits. Published studies have used at least a 75 percent change in relief of pain before a response is considered positive and the sacroiliac joint deemed the source of pain. However, several other injection studies have compared intra-articular with extra-articular injection, and indicate that the ligament injection behind the joint is oftentimes superior to injection in the joint and seems to be a very underutilized diagnostic tool.
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.