Understanding Your Spine & How to Keep it Healthy – Part 2 (Sacroiliac Joint)

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Understanding Your Spine & How to Keep it Healthy – Part 2 (Sacroiliac Joint)

The sacroiliac joints (SI) connect the sacrum, the triangular shaped bone at the base of the lumbar spine to the left and right iliac bones, the large bones that form your pelvis.

The SI joints have several functions

  • They support the weight of your torso when you are upright
  • They help maintain balance as you walk
  • They act as shock absorbers for your spine
  • They act as a hub for the transfer of force between your legs and your torso

They are designed as a stable joint with limited mobility.

Movement includes

  • Nutation or anterior tilt (flexion) of the sacrum between the ilia
  • Counter-nutation or posterior tilt (extension) of the sacrum between the ilia
  • Small movements of the ilia themselves

Stability of an SI joint depends primarily on the stout ligaments that cross it, but there are also bony stabilisers, static soft tissue and dynamic muscular stabilisers as well as fascia. The ligament stabilisers occur on the anterior (front) and posterior (back) of the joint and include

  • the sacrotuberous ligaments connecting the sacrum to the ischial tuberosity (sit bones)
  • the sacrospinous ligaments connecting the sacrum to the posterior iliac spine

Interaction between the erector spinae muscles and the pelvic floor is also important for stabilising the SI joints.

The erector spinae (Spinalis, Longissimus, Iliocostalis) draw the sacrum into flexion and the muscles of the pelvic floor draw the sacrum into extension. Simultaneously engaging these muscles creates opposing forces that stabilise the joints.

It is also worth mentioning that the SI joints are synovial joints and can be affected by whole-body conditions (gout, ankylosing spondylitis) that result in joint inflammation.

What is Sacroiliac Joint Pain?

The SI joint is a major contributor to low back pain, affecting between 15-25% of low back pain sufferers.

Common Symptoms include

  • Dull, achy lower back pain below the L5 level
  • Pain that radiates to the hips, groin, and/or buttocks
  • Numbness and tingling that may radiate into the buttocks and/or thigh, but rarely below the knee
  • Stiffness and decreased range of motion in the lower back, pelvis, hips and groin
  • Increased pain when pressure is applied to the affected SI joint or lying on the affected side

Possible Causes of SI Joint Pain

Too much movement (hypermobility or instability) in the SI joint can cause the pelvis to feel unstable and lead to pain, typically felt on the low back and/or hip and may radiate to the groin area.

Too Little movement (hypomobility or fixation) can cause muscle tension, pain, and inhibit mobility. Pain is typically felt on one side of the low back or buttocks, and can radiate down the back of the leg (similar to sciatic pain).

Other Possible causes of SI Joint Pain

  • How you walk
  • Repetitive pounding pressure from exercise such as running or contact sports
  • An injury or trauma to the ligaments that surround the SI joints
  • Previous spine surgery
  • Hip joint replacement & spine fusion
  • Pregnancy & childbirth
  • Postural abnormalities such as scoliosis & uneven leg length
  • A herniated disc
  • Spinal stenosis
  • Osteoarthritis
  • Bursitis of the hip
  • Obesity

Activities that put pressure on the sacroiliac joints include

  • Golf
  • Tennis
  • Football
  • Crunches and sit-ups
  • Cycling
  • Weightlifting
  • Contact sports

What can you do?

  • Massage therapy
  • Stretching exercises
  • Strengthening exercises
  • Hot and cold treatments to relax the muscles and ease pain
  • Wearing a sacroiliac belt to support the joints
  • For inflammatory conditions, whole body therapies may be required

SI Joint Exercises focus on stabilising and strengthening the muscles around the SI joint

  • Gluteus maximus
  • Gluteus medius
  • Piriformis
  • Pelvic floor muscles
  • Core muscles

You’ll be familiar with some exercises we practice in class, including


Squeezing a Studio Ball between your knees

Hip Abduction using a Resistance Loop

Basic & Advanced Bird Dog

Double Knee to Chest Stretch

Single Knee to Chest Stretch

Child’s Pose

Supine Spinal Twist


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