What are the Sacroiliac joints?

The sacroiliac (SI) joints in the pelvis are the foundation on which the spine rests, and play an important role in transmitting and distributing the weight and forces of the body, as well as the compression forces on the spine down the legs. They are strong and designed to withstand large stresses and strains. 

The Sacroiliac joints join the spine to the pelvis and hips.  They comprise of the Sacrum, the tail bone and the Ilium bones, and commonly they are called ‘SI’ joints, or ‘pelvic’ joints, which should not be confused with hip joints that are lower. They are found below the waist at the bottom of the spine, above the buttocks, and can feel like two dimples when pressed. 

Sacroiliac joint injuries are a very common cause (16-30%) of lower back pain, and one which Chiropractors are experienced at treating. 

How do the Sacroiliac joints work? 

Sacroiliac joints stabilize the spine, and are semi-moveable joints. Movement is minimal and limited to about 2-4mm of gliding and rotation. Anatomy books in the past sometimes disagreed about how much movement exists in the sacroiliac joints, saying they were ‘fixed’ or immoveable, but they do now recognise they move a little.  The sacroiliac joint is jagged and irregularly-shaped between the sacrum and the ilium. The upper one-third is a semi-movable joint (syndesmosis) with connective tissue, while the lower two-thirds are lined by articular cartilage, with synovial fluid and lined by fibrocartilage.  Sacroiliac joint surfaces are smooth in juveniles and become irregular over time, clearly reducing in movement with age. 

Any Chiropractor (and many clients who’ve been helped by having them adjusted) would argue that some movement, pliability or elasticity is essential to good health, treatment and prevention of low back pain. 



The sacroiliac ligaments tend to be stiffer in men than women, in whom they are able to separate for childbirth, which can cause some laxity in the joints and to which many women attribute the onset of their back pain. It’s suggested women perhaps are more affected than men since they tend to have more flexibility of their ligaments, however, men lift and strain their back more in general and so put greater stress on the joints. In my experience it’s fairly equal in men and women. 

Common causes of sacroiliac joint pain  

  • Injury or trauma producing ligament laxity, often a combination of vertical compression and rapid rotation (e.g. carrying a heavy object or twisting), or by a fall on the backside or a car accident. 
  • Prolonged sitting is the main culprit, especially when the forces are increased with poor posture, causing muscle imbalance and weakness, which silently, with no pain, puts stress on the joints. 
  • Repeated small strains like lifting, twisting, carrying a baby, usually on the same hip, often giving no pain until the ‘final straw’, a commonly innocuous movement like just bending to pick up something on the floor causes an acute back strain. 
  • Pregnancy or a traumatic birth. In the last three months (or even earlier) in pregnancy the hormone ‘relaxin’ is released to increase the laxity of the pelvic ligaments to allow them to separate for childbirth, which can make them more vulnerable to injury, along with the extra weight of the foetus. 
  • Restricted movements in the lumbar or upper spine, and hips and knees particularly, all add increased pressure to the sacroiliac joint. 

Strain to the joint capsule causes microscopic ligament tears, which then becomes inflamed and painful, and causes the muscle in the body to tighten and ‘protect’ the spine to prevent more damage.  This muscle spasm lasts longer than required and causes considerable pain. Often patients find they are twisted or locked to one side in Antalgia. The most common spasms are the piriformis, gluteal or buttock and psoas muscles. 

Signs and Symptoms of Sacroiliac (SI) Joint Sprain 

  • Pain around one or both SI joints and into the buttocks. 
  • Pain can ‘move’ from left to right, switching from side to side. 
  • Radiating pain into the front or back of the thigh or groin. 
  • Sitting can be painful. 
  • After sitting, the back can feel ‘locked’ in antalgia and you feel you can’t straighten with the first few moments or steps being painful. 
  • Pain when putting weight on one leg, or the leg feels as if it could ‘give way’ 
  • Pain on bending forward 
  • Loss of strength in lower leg, pins and needles or numbness. 

Sacroiliac joint referred pain 

Referred pain from the sacroiliac joints is commonly to the back of the thigh, which can confuse clients into thinking this is sciatica. 

Referred Pain Study 

Sacroiliac joints have variable referred pain patterns, reproduced by fluoroscopy-guided sacroiliac joint injections, commonly lower back pain, buttock and posterior thigh, but rarely lower leg pain, according to this article from Pubmed.  

See also an informative article about sacroiliac joint pain.



Chiropractic treatment and diagnosis of a Sacroiliac joint sprain 

The diagnosis is usually based on clinical findings.  Chiropractors use motion palpation to evaluate how the pelvis and sacroiliac joints are moving, postural visualisation, orthopaedic and muscle tests to make a clinical diagnosis, along with the history and signs and symptoms. 

If the condition is acute, the Chiropractor’s focus is on reducing inflammation, inducing movement into the sacroiliac joints (as they will invariably be tight and stiff) with manipulation or adjustment to the joints. That could mean a full manipulation or adjustment or gentle mobilization techniques, as well as deep massage and muscle releasing to the surrounding muscles in spasm. 

Anti-inflammatory drugs (NSAIDS) should be used sparingly, only in the intense acute phase for short periods as they do not help the healing process, and may in fact slow or prevent proper healing. 

Sacroiliac joint pain moving from side to side, left to right. 

It’s very common for clients to have pain wandering from one sacroiliac joint to the other, from side to side, left to right.  It’s also very common during Chiropractic treatment for the sacroiliac joint pain to move from one side, to the other, then back to the original side.  I’ve lost count of how many times clients report this. Usually as the condition settles, the pain lessens as it moves from side to side.  The pelvic joints work together and it’s not possible to affect the movement and balance of one side without affecting the other. My analogy is that of adjusting hinges on a door: that when you adjust one hinge, commonly the other hinge will need to be adjusted, then the first hinge again, to balance the door freely. 

Sacro-iliac joint Pain 

(ie pain on right) 

Door not swinging freely 

(ie door rubbing at top) 

Treatment to right side  Adjust top hinge 
Pain moves to LEFT side 

(less pain) 

BOTTOM hinge out 

(not as badly out of alignment) 

Treatment to Left  Adjust bottom hinge 
Pain moves back to RIGHT side 

(even less pain, improving) 

TOP hinge 

requires further adjustment 

Pain settles  Door swings freely 

 Patient education with Sacroiliac joint issues 

An important part of treating sacroiliac joints is teaching the patient how to avoid restraining the joints or causing a recurrence of the symptoms: 

  1. Avoid bed rest and prolonged inactivity 
  2. Avoid sitting too long or in a poor position which can put a constant strain on the joints. Learn how to vary your work positions, using a sit-stand desk, resting the back, walking or using a movement stool to induce movement into the joints and help the core flexibility 
  3. Stretching exercises to release the gluteal muscles 

Sacroiliac joint self-help 

  • Lying down to rest the back for short periods can ease the pain, making sure you are comfortable, either resting the back with the knees bent or on your side in the recovery position with a cushion or pillow under the top knee. Don’t get set or lie for too long before getting up to move around. 

The general recommendation is to make sure you get the problem diagnosed properly; have a chiropractor evaluate your core stability, have treatment if necessary and do the right type of exercise to help your problem. 

Factors affecting sacroiliac joint recovery 

  • The severity of the injury and strain. 
  • Duration: how long it has been there, the past history. 
  • The number and severity of previous episodes, which can progressively weaken ligaments.
  • With increasing age, the sacroiliac joints clearly wear and have more scar tissue with less movement. 
  • Poor posture and being too sedentary. 

Sacroiliac pain vs hip pain 

Sacroiliac pain can often be closely related to hip pain, or the two occur together. 

Pain can radiate from the sacroiliac joint to the groin and the muscles around the pelvis and hip, and sacroiliac joints can be tight or in spasm, so can sometimes confuse where the pain is coming from. 

Generally a Chiropractor, with a careful diagnosis, can distinguish between the two conditions.  Here are some guides as to the different symptoms: 

Pelvic sacroiliac joint Pain  Hip Pain 
Pain sitting or pain after sitting  Sitting relieves pain 
Better for walking and movement  Worse on walking 
Better for swimming and non-weight-bearing exercise  Better for swimming and non-weight-bearing exercise 
X-rays are not usually helpful  X-rays are a good diagnostic test 
Referred pain into thighs  Referred pain into knee 
Pain more in back and buttock  Pain more on side of hip 
Hip movement good  Reduced hip range of movement 
No pain on hip movement  Pain on hip movement 


Symphysis pubis dysfunction (SPD) 

Pubic symphysis disorder is closely related to sacroiliac joint dysfunction and misalignment of the pelvis. It’s mainly pregnancy related. Treatment of the sacroiliac joints can help tremendously to reduce the strain on the pubic symphysis and reduce the pain from the SPD.  Full article: Symphysis pubis dysfunction 

Other causes of sacroiliac joint instability 

  • Lumbar spine surgery in which a large portion of the ilio-lumbar ligament is injured 
  • Length leg discrepancy (one leg shorter than the other) 
  • Gait abnormalities 
  • Prolonged vigorous exercise 
  • Traumatic pregnancy or birth 
  • A long scoliosis or curve in the spine 
  • Fusions where the lumbar spine can ‘fuse’ to the sacrum. 

Medical Causes of sacroiliac joint pain 

There are various medical causes of sacroiliac joint pain, which can be diagnosed with blood tests, X-rays, or MRI scans. 

  • Sacroilitis – inflammation in the sacroiliac joints, showing on X-rays 
  • Arthritis from autoimmune disorders such as: 
  • Ankylosing spondylitis, juvenile rheumatoid arthritis 
  • Reiter’s Syndrome, psoriatic arthritis 
  • Infections like staphylococcus, gonorrhoea, Tuberculosis (TB)

X-rays for the sacroiliac joints are usually not that helpful; the shape and angle of the joint makes it difficult to see clearly. X-rays for the back may help to rule out other underlying causes.