Visualising the sacro-iliac joint

The sacroiliac joint is a vital component of the human skeletal system, connecting the sacrum (the triangular bone at the base of the spine) to the ilium (part of the pelvic bone). It is often referred to as the SIJ ( sacroiliac joint). It serves a crucial role in transferring forces between the upper body and lower extremities, providing stability and facilitating movement. It is a complex joint, and can create issues in us all, from women in pregnancy and post natal days, sportsmen and women, runners, and those with lower back or lumbar issues. IT has been reported that up to 70% of those suffering from persistent lower back pain will have some element of their pain stemming additionally from the SIJ.  

As the SIJ is a huge weight transfer 'station' for loads passing  from our lower extremities to our trunks, the joint is reinforced by many strong ligaments and surrounded by muscles that help support the pelvis and spine.

These reinforcements give the joint incredible stability to cope with the transmission of upper body weight and forces from the spine to the lower extremities during activities such as walking, running, and lifting. It absorbs shock and redistributes forces, ensuring efficient movement and minimizing stress on other joints.

Despite this stability, the SIJ is prone to dysfunction and pain. Injuries, arthritis, pregnancy, or imbalances in the surrounding muscles can lead to dysfunction of this joint, causing pain in the lower back, buttocks, or legs. Diagnosis and treatment of SIJ issues often involve a combination of physiotherapy and exercise. Long rehabilitation programs are often required to improve the muscular support and stability of this very important joint. These programs need to be sport specific, or tailored to each individual's needs and can include core stability, pelvic alignment exercises, postural stability and gluteal strength. 

"Anchor through your tailbone when you are on the mat"

This Pilates cue is a common one when it comes to ensuring your alignment and control of your 'pelvis and spinal neutral' postures in class. This is especially so when testing your deep abdominal strength in exercises such as table top. But what does this 'tailbone' actually look like? It is anatomically called the sacrum and may not look like what you imagine.

I often get asked about the coccyx with reference to this Pilates cue. When you study this image, you can see that your coccyx is just the tiny bone on the end of the sacrum. it is not through this that you find or control your 'pelvis neutral' of 'heavy tailbone.'   

The sacrum articulates with the iliums of the pelvis on each side. These 2 joints are called the sacro-iliac joints ( you have a left one and a right one), and these are crucial role in providing stability, transmitting forces, and facilitating movement between the upper body and lower extremities.    

The pubic symphysis joint is a specialized joint located in the pelvis, specifically between the left and right pubic bones. It connects the 2 halves of the pelvis.  The joint is composed of fibrocartilage, which provides strength and stability while allowing slight movement.

The pubic bone itself is a thick, flat bone that forms the lower part of the front of the pelvis. It serves as an attachment site for various muscles, including the adductor (groin) muscles of the inner thigh, the abdominal muscles and the pelvic floor muscles. (You could think of the pubic symphysis and the coccyx as the 2 fixed ends of your pelvoc floor 'hammock'. Together, the pubic symphysis joint, along with the surrounding pelvic floor muscles, play a crucial role in maintaining pelvic stability and supporting the pelvic organs. During activities such as walking, running, and standing, these structures work together to provide strength and control to the pelvis.