Dooley Noted: 4/28/2015
The sacroiliac (SI) joint is an enormously stable joint that has both fibrous and fully moveable components.
The auricular surfaces of both the ilium of the hip bone and the sacrum articulate to form this joint.
Even in our youth, this joint seeks more stability than mobility.
The anterior and supremely dense posterior sacroiliac ligaments anchor the bones to each other, while serving as anchor points to important ligaments attaching to the ischial tuberosity (via the sacrotuberous ligament), to coccyx (via the sacrotuberous and dorsal sacrococcygeal ligaments, and to the lower lumbar spine (via the iliolumbar ligament).
The SI joint features a special internal ligament called the interosseous ligament, helping to prevent excessive mobility as the SI stabilizes the pelvis. This adds to the fibrous nature of this joint.
The feed to the SI joint comes from the posterior division of the internal iliac artery.
The innervation to the SI joint is controversial in the literature. The studies can agree that this massive joint receives overlapping innervation from many lumbosacral nerves, which include the following: the obturator nerve (L2-L4), and the lumbosacral trunk (L4-L5), the superior gluteal nerve (L4-S1), and the first few sacral ventral rami.
The SI joint has limited movement, with a forward and backward tilting called nutation and counternutation, respectively. Due to its thick attachments, the joint is permitted less than 2 degrees of transverse plane rotation.
Connections from the SI joint ligaments blend with the iliolumbar ligament, the same attachment for both the quadratus lumborum and iliacus muscles. These two muscles serve as enormous stabilizers for this joint.
If a muscular imbalance occurs between one of the two muscles, stability dynamics for the SI joint are altered. Most frequently, this results in an anterior pelvic tilt, which compresses the anterior aspect of the SI joint. Pain is often perceived in the posterior part of the joint, which is being stretched.
To gap the joint and return it to a less compressed position, one must assess for muscular imbalances and SI joint decompression. This same presentation is usually referred to as “lower cross syndrome.”
In this presentation of SI joint compression, the most common culprits of concentric contraction (muscle shortening) are the following:
– facilitated iliacus
– facilitated erector spinae
– facilitated quadratus lumborum (although this can be inhibited by erectors)
– facilitated piriformis
– facilitated coccygeus (via the sacrospinous ligament)
Commonly inhibited muscles in this presentation match the “lower cross syndrome” presentation and include the following:
– inhibited abdominals, especially transversus abdominis and rectus abdominis
– inhibited multifidii lumborum
– inhibited gluteus maximus
– inhibited psoas major
Remember: when muscles fail, the ligaments must then hold on for dear life. They are not as dynamic as the muscles, and they lack the copious blood supply afforded to the muscles.
But, the ligaments have proprioception and some nociception. And joint alterations can certainly increase joint capsule tension posterity, increasing the potential for pain perception.
So, yes – you can feel them.
Irritated ligaments require an inflammatory process to heal. They also require the muscles to start to work in synergy again to maintain dynamic architecture as the ligaments heal.
The reverse can also happen, especially with trauma and pregnancy. The SI joint ligaments can become lax, allowing for more rotational movement than is normally permitted. The muscles may not have time to develop the motor control to adjust to the new range of motion. This can also result in SI joint decompression, matched with discomfort at the SI joint.
If working with the traumatically injured or pre/post natal SI joints, special care just be taken to teach the client on how to better use adjacent joints, like the lumbar spine and hip.
By learning abdominal stability, the SI joint will not be able to move as freely at the iliolumbar ligament and lumbosacral joints.
By learning proper hip control, the SI joint will be asked to stabilize for the hip that requires mobility. Proper squatting and hip hinging techniques are wonderful for this population, especially since they have trouble getting out of bed or getting out of chairs.
Consider seeing a movement specialist if your SI joint pain is just not leaving.
As always, it’s your call.
– Dr. Kathy Dooley