The sacroiliac joint (SIJ) connects the sacrum with the pelvis. The sacrum is the triangular bone located at the bottom of the spine and it joins with the iliac bones that comprise part of the pelvis. The SIJ is very important in transferring all the forces of the upper body to the pelvis and legs. There is not a lot of motion in the joint and it is very strong and stable. The limited motion at the SIJ decreases with age and increases with pregnancy.
The SIJ is stabilised by a network of ligaments and muscles, which also play a role in limiting the motion in all planes of movement. The normal SIJ has a small amount of motion approximately 2-4mm of movement in any direction. In some people due to trauma or just extra mobility, the SIJ has too much uncontrolled motion. This allows the SIJ to adopt an abnormal or stressed joint position, which may result in SIJ pain. The sacroiliac ligaments in women are less stiff than men’s, allowing the mobility necessary for childbirth.
Mechanical strain and injury to the SIJ are produced by either a combination of vertical compression and rapid rotation (i.e. carrying a heavy object and twisting), or by falls on the backside. Injuries of this type can produce ligamentous laxity and allow painful abnormal motion. Instability can also arise from lumbar spine surgery in which a large portion of the ilio-lumbar ligament is injured. SIJ pain can also be caused by leg length discrepancy, gait abnormalities, prolonged, vigorous exercise, traumatic birth, and long scoliosis fusions to the sacrum.
Due to the complex nature of the SIJ and its surrounding structures, treatment of SIJ dysfunction must focus on the entire area including the abdominals, lumbar spine, sacrum, pelvis and hips. Treatment would focus on addressing joint, muscular, neural and fascial restrictions and deficiencies. A core stability program is very important and aims at improving the strength and activity in the pelvic floor, transverses abdominus, gluteal muscles, and the latissismus dorsi. These muscles cross the SIJ adding to the joints stability so dysfunction in this group will contribute to SIJ pain. SIJ belts and taping are useful treatment aids that help to reduce excessive joint movement and decrease pain. These are very common tools used in the management of pregnancy related SIJ pain.