Sacroiliac Joint Ligaments and Muscles

The sacroiliac (SI) joints are two joints that link the lower spine to the pelvis. When in a standing position, these joints support the weight of the whole upper body. They also play a crucial role in mobility, balance, and function in the lower back. If you’re suffering pain or stiffness in the hips and lower back, it may be related to a dysfunction affecting the SI joint. To understand the role of these joints and how to approach dysfunction, you should understand their structure. Below, we discuss SI muscle and ligament structure.

Sacroiliac Joint Muscles

The muscles around the SI joint do not specifically power the movements in the pelvis and lower back. The movements around these joints are powered by the tension in their ligaments.  The sacroiliac joint SI joint muscles primarily play the role of providing stability. There are more than 40 muscles around the sacrum region. However, the main muscle groups that have an actual impact on the joint are:

• The back muscles include the quadratus lumborum, multifidus lumborum, and the erector spinae.
• The muscles in the core include the rectus abdominis.
• The hip muscles including the iliopsoas
• The muscles in the thigh including the hamstrings and biceps femoris.
• The muscles in the buttocks including the piriformis and gluteus maximus.

Tightness in an SI joint muscle can occur due to inadequate activity. This is common among people who live a sedentary life. The muscle(s) become shorter. This causes increased tension around the joint. It becomes stiff as a result. You may also experience pain in this region. Stretching can help to elongate the muscle reduce tightness and restore function.

Sacroiliac Ligaments

As mentioned earlier, the sacroiliac muscle groups don’t move the joint but are important for stabilization. Movement comes from tension in the ligaments. The ligaments are important for stabilization, support, and movement. They include:

• Interosseous ligament

One of the strongest ligaments in the entire body, it connects the inner surface of the hip bone (ilium) to the outer surface of the lower spine (the sacrum).  This ligament bears significant loads while supporting movements in the lower body and stabilizing the torso. It prevents movement of the sacrum in a forward or backward direction.

• Anterior sacroiliac ligament

Also known as the ventral sacroiliac ligament, this ligament includes the articular capsule. It encloses the joint and does not play a supportive role. It is in fact quite thin and vulnerable to injury.

• Superior intracapsular ligament

This ligament offers little mechanical value. It is believed to be part of the interosseous ligament and isn’t always present.

• Accessory ligaments

Three accessory ligaments are vital for enhancing the stability of the joint. These are the iliolumbar, sacrotuberous, and sacrospinous ligaments. The sacrospinous and sacrotuberous ligaments together create the greater and lesser sciatic foramen. The sciatic nerve, the largest nerve in the body, passes through the greater sciatic foramen.

Nerves in the Sacroiliac Joint Area

One of the many reasons why dysfunction in this region can result in tremendous pain is because the area is well-innervated. It should be noted that the pattern of the nerves supplying the area varies from one individual to another. The distribution of nerves is also not always uniform on the left and right sides of the same person’s body.  Scientists believe this is the cause of diverse pain patterns in patients with sacroiliac dysfunction.

Sacroiliac Joint Surgery Bellevue & Redmond

If you suffer from sacroiliac dysfunction and pain don’t hesitate to get in touch with us, Dr. Chris Boone, MD. Schedule a consultation and get an accurate diagnosis for the cause of your pain, discomfort, and loss of function or mobility. Get answers to your questions and start your journey to improving your quality of life.