Sacroiliac joint

The Sacroiliac joint (SI joint) is a critical component of the human skeletal system. It is located in the pelvis, linking the ilium (part of the pelvis) to the sacrum (the final segment of the spine). The primary function of the sacroiliac joint is to absorb shock between the upper body and the pelvis and legs, providing stability and lessening the impact on the spine.

Anatomy

The sacroiliac joint is a synovial joint, a type of joint that is surrounded by a thick fibrous sac called the joint capsule. The joint capsule is filled with synovial fluid, which lubricates the joint and aids in movement. The joint is supported by a system of ligaments, including the anterior and posterior sacroiliac ligaments, the interosseous sacroiliac ligaments, and the sacrotuberous and sacrospinous ligaments.

Function

The sacroiliac joint's primary role is to transfer weight and forces due to movement from the spine to the lower extremity. It also acts as a shock absorber, reducing the impact of steps or jumps on the spine. The joint allows for minimal movement, which is necessary for activities such as walking or running.

Clinical Significance

Dysfunction or inflammation of the sacroiliac joint, known as sacroiliitis, can cause significant pain and disability. This condition can be caused by a variety of factors, including arthritis, pregnancy, trauma, or infection. Treatment options for sacroiliitis include physical therapy, medication, and in severe cases, surgery.

See Also

• Pelvis
• Spine
• Sacroiliitis
• Arthritis

References

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