Sacroiliac Joint Pain

The sacroiliac (SI) joint has an important function, transferring the weight of the upper body from the spine to the lower body.  It connects the spine to the pelvis by joining the sacrum to the iliac (pelvis bone).

The sacrum is a triangular shaped bone centrally located beneath the lumbar spine, it is made up of five fused vertebrae which don’t move and is connected to the iliac bones on both the right and left-hand side, by the SI joint.

sacoiliac join example

Understanding Sacroiliac Joint Composition

Like all joints in the body, the SI joint is surrounded by a layer of soft tissue. It is both a synovial and fibrous joint, encapsulated by a synovial membrane which produces synovial fluid. This serves to lubricate the joint and facilitate movement. Although the SI joint is small, it is extremely strong, reinforced by the surrounding ligaments which extend from the joint capsule to anchor the bones in their correct position. The SI joint is lined by fibrocartilage – a strong type of cartilage with shock absorbing properties, found predominately in intervertebral discs, connective joints and ligaments.


SI joints are comparatively stiff and rigid, they do not bend or flex and allow only for minimal movement, limited to gliding and rotation – this is to prevent dislocation and maintain the joints in their position. The SI joints also act as shock absorbers, limiting the transfer of impact between the spine and the pelvis.

What Causes Sacroiliac Joint Pain?

SI joint pain refers to pain associated with the sacroiliac joint region, it may be local or referred (felt in another part of the body, such as the buttocks or hamstrings in the legs), painful symptoms are usually the result of changes to the joint SI joint dysfunction, or Sacroiliitis – inflammation of the soft tissue structure of the joint.  SI joint dysfunction is caused by abnormality of movement and can generally be grouped into two categories:

Hypermobility – this refers to excessive movement and instability

Hypomobility – this refers to stiffness and a reduction of movement

Causes of Sacroiliac Joint Pain


Pregnancy hormones such as relaxin and progesterone are released in preparation for childbirth to allow ligaments and muscles particularly in the pelvic region, to relax. This can lead to increased movement, over stretching the joints and muscles and resulting in instability. The altered walking pattern and additional weight gain caused by pregnancy can also strain the joints and cause inflammation, often resulting in painful symptoms in the posterior pelvis, such as a burning sensation or deep ache – the pain may on some occasions, rotate to the groin and legs.


Degenerative arthritis and rheumatoid arthritis are both possible causes of SI joint pain and inflammation. The wear and tear of the ageing process, excessive weight and repetitive motion can cause the degeneration or inflammation of joints, ligaments and bones.

Ankylosing Spondylitis is a type of arthritis effecting the spine and causing inflammation in the joints – sacroilliitus is often one of the symptoms of the condition.


A trauma which effects the hips, buttocks or lower back, such as a fall or even a vehicle accident can injure the SI joint causing inflammation or joint dysfunction.

Mechanical Stress

Having another pre-existing condition in the lower back such as an abnormality of the sacrum – (vertebrae which haven’t fused together), can cause mechanical problems with the SI joints. Mechanical stress may also be caused by a leg length discrepancy, in which case poor postural alignment and altered gait pattern can result in uneven wear and tear on the SI joints and other components of the lower back.

Symptoms of SI Joint Complications

Frequently reported symptoms include pain felt in the lower back, pelvic region, buttocks, it may even radiate as far as the hamstrings. Pain can be anything from a dull ache or sharp stabbing pains which may worsen when leaning forwards, or rising from a sitting to a standing position. Balance and gait may also be altered.


A thorough physical examination involving specific movements of the joint with a history of the symptoms is essential, MRI and SPECT CT scans can also be useful diagnostic tools for determining if indeed the SI joint is the cause of the painful symptoms, as well as for ruling out other symptoms.

Diagnosis can be tricky, as many of the symptoms mimic those of other pain related conditions involving the back.

Sacroiliac Joint Pain Treatment

Possible treatments include:


Sacroiliac Joint injections with corticosteroids using X-Ray guidance are administered to the joint providing pain relief for up to several months in some patients.

Radiofrequency Denervation

Usually used for treating facet joints, radiofrequency denervation can also be useful in the treatment of SI joints. This form of treatment uses heat to deactivate the nerves surrounding the painful joint, preventing it from sending pain signals.


Specific exercises can be very useful for loosening stiffness as well as strengthening, a good physio therapist can also help correct posture and body movements, and provide advice on different sleeping positions.

Pain Medication

Over the counter medication can be used to treat painful symptoms and in more severe cases, prescription painkillers may be administered.


In some cases, where all the above treatment methods fail, then surgery may be considered as an option. SI joint fusion permanently fixes the sacrum to the ilium using metal implants.

How Dr. Miller Can Help

Here at the Pain Management clinic we offer individualised treatment for our patients taking into consideration not only the biological symptoms, but also social and psychological interactions. Dr Miller works closely with a multidisciplinary team of surgeons, physiotherapists, psychologists and other health professionals, enabling him to offer high quality individually tailored patient care.

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