The Sacroiliac joints are located in the lower area of the back. The sacral bone consists of 5 fused vertebra with the tail bone(coccyx) at the end. The sacroiliac joints are on ether side the sacral bone and join the spine to the pelvis.
The function of the SI joints is to allow twisting movements of the pelvic bone when we move our legs. The legs act like levers and along with the pubic bone (at the front of the pelvis),allow these movements.
Dysfunction of the sacroiliac joint refers to either hypo (locked) or hyper (too much) mobility. This can then lead to problems with surrounding astructures such as the iliolumbar ligaments and gluteal as well as other pelvic muscles. SIJ problems can cause a wide range of symptoms throughout the lower back and buttocks, or even the thigh or groin.
Symptoms of SI Joint injury includes pain located either to the left or right of your lower back. The pain can range from an ache to a sharp pain which can restrict movement. The pain may radiate out into your buttocks and low back and will often radiate to the front into the groin. Occasionally there may be referred pain into the lower limb which can be mistaken for sciatica.
Classic symptoms are difficulty turning over in bed, struggling to put on shoes and socks and pain getting your legs in and out of the car. Stiffness in the lower back when getting up after sitting for long periods and when getting up from bed in the morning. Aching to one side of your lower back when driving long distances. There may be tenderness on palpating the ligaments which surround the joint.
Causes of Sacroiliac joint pain can be split into four categories:
Traumatic : injuries to the SIJ are caused when there is a sudden impact which 'jolts' the joint. A common example is landing on the buttocks. This kind of injury usually causes damage to the ligaments which support the joint.
Biomechanical : Pain due to biomechanical injuries will usually come on over a period of timeand often with increased activity or a change in occupation/sport etc. The most common biomechanical problems include:Leg length discrepancy,Overpronation of the feet,'Twisted pelvis' and Muscle imbalances
Hormonal : Hormonal changes, most notably during pregnancy can cause sacroiliac pain. In preparation for giving birth, the ligaments of the pelvis especially increase in laxity. Combining this with an increase in weight putting extra strain on the spine, may lead to mechanical changes which can result in pain.
Inflammatory joint disease: Spondyloarthropathies are inflammatory conditions which affect the spine. These include Ankylosing Spondylitis which is the most common inflammatory condition to cause SI joint pain.