How Sacroiliac Joint Strain Occurs

The sacroiliac joint is the joint that attaches the sacrum to the hipbone, one on each side. Sprains and strains to the ligaments of the sacroiliac joint are one of the most common causes of back pain, along with degeneration of the intervertebral discs.

The sacroiliac joint, or SI joint is the joint in the bony pelvis between the Ilium and the sacrum of the pelvis, which are joined together by strong ligaments. In humans, the sacrum (along with the coccyx below it), make up the bottom of the vertebral column; and it protects the spine. The joint is a strong, weight bearing and shock absorbing synovial joint that connect the three bones together and provide a stability to the spinal column. a person has two Sacroiliac, or SI, joints on either side. The two SI joints main job is to hold the sacrum in place, and there is very little movement in these bundles of ligaments when healthy. The joints connect the three bone structures between the articular surfaces of the Ilium and sacrum bones. The pair of SI joints move together as a single unit to hold the sacrum and spinal column in place. The joints are covered by fibrocartilage on the ilial surface and hyaline cartilage on the sacral surface. As we age, or when we put added pressures on the pair of SI joints, the structure may undergo changes that include a loosening of the ligaments.

There are several ligaments that attach the Ilium to the sacrum on each side. These ligaments include the Sacrospinous ligament, Sacrotuberous ligament, Posterior sacroiliac ligament, Interosseous sacroiliac ligament, and Anterior sacroiliac ligament. There is some degree of contention in the medical community as to how much sacroiliac joint dysfunction contributes to back pain. Generally, the main job of these ligaments is to hold the sacrum in place and secure it to the Ilium on each side of the hip. Many specialists think that only under trauma can these ligaments become strained enough to cause back pain. Others, especially chiropractors, disagree, insisting that SI joints do move and that strains of these joints can be a significant cause of lower back pain. Chiropractors often do manipulations on the SI joints to treat strains on these joints when appropriate. Orthopedic physicians at pain management clinics will sometimes use sclerosing injections to tighten up lax ligaments of the SI joints.

Here are some symptoms of low back pain caused by sacroiliac joint strain.
  • The pain is typically on one side of the lower back, hip, and leg (the pain can be occasionally bilateral)
  • While lumbar nerve root pain may project all the way to the foot, SI joint pain seldom radiates to the lower leg. SI joint pain is typically contained to the hip, groin, and above the knee.
  • Mechanical sacroiliac joint dysfunction typically causes a dull lower back pain.
  • Pain and stiffness associated with SI joint symptoms is exacerbated by extended periods of sitting or walking.
  • The pain may worsen by certain physical activities, such as lifting the knee up during stair climbing or sitting up after being seated for a certain period of time.