Sacroiliitis and Sacroiliac Joint Pain.
What is sacroiliitis?
Sacroiliitis refers specifically to inflammation of the sacroiliac joints — the two joints connecting the sacrum (the triangular bone at the base of the spine) to the ilium (the large wings of the pelvis). These joints bear significant load in standing and walking, transmitting forces between the spine and the lower limbs, and are stabilised by some of the strongest ligaments in the body.
Sacroiliitis is distinct from the broader term sacroiliac joint dysfunction (SIJD), which describes mechanical dysfunction of the SIJ without necessarily involving active inflammation. Sacroiliitis implies a specific inflammatory process within the joint — either from an inflammatory arthropathy, infection, or significant mechanical overload — and its management reflects this distinction. That said, in clinical and everyday usage the two terms are often used interchangeably, and many people presenting with SIJ pain have elements of both.
What causes sacroiliitis?
The most clinically significant cause is inflammatory arthropathy — systemic inflammatory conditions that cause joint inflammation as part of a broader disease process. Ankylosing spondylitis (now classified as axial spondyloarthritis) is the condition most strongly associated with sacroiliitis, characteristically producing bilateral SIJ inflammation that is often the earliest manifestation of the disease. Psoriatic arthritis, reactive arthritis, and inflammatory bowel disease-associated arthritis can also produce sacroiliitis. In these conditions, sacroiliitis is not a mechanical problem but a systemic one requiring medical management alongside physiotherapy.
Mechanical sacroiliitis — where the joint becomes inflamed from biomechanical stress rather than a systemic disease — is also well recognised. Pregnancy and the postnatal period, leg length discrepancy, scoliosis, previous spinal surgery, and sports with repetitive asymmetric loading are all associated with mechanically-driven SIJ inflammation. Pelvic girdle pain during and after pregnancy frequently has a significant sacroiliac component.
Infective sacroiliitis — bacterial infection of the SIJ — is rare but serious and requires urgent medical management rather than physiotherapy. It should be considered when sacroiliac pain is accompanied by fever, constitutional symptoms, or a history of intravenous drug use.
What are the symptoms?
Pain in the lower back, buttock and posterior pelvis is the hallmark symptom, typically unilateral (one side) in mechanical presentations and bilateral in inflammatory arthropathy. The pain may refer into the groin, thigh or even the calf, mimicking sciatica or hip pathology.
Stiffness is characteristic, particularly in the morning — in ankylosing spondylitis, morning stiffness lasting more than 45 minutes that improves with movement is a diagnostic hallmark. Pain is typically provoked by prolonged standing, walking, climbing stairs, rolling over in bed, and transitioning from sitting to standing.
How is sacroiliitis diagnosed?
Clinical assessment includes specific provocation tests for the SIJ — the FABER test, posterior pelvic pain provocation test (P4 test), Gaenslen's test and thigh thrust test — alongside evaluation of lumbar spine and hip mobility. The pattern of positive and negative tests helps differentiate SIJ from lumbar spine and hip pathology, though the three often coexist and all need to be assessed.
Imaging for sacroiliitis depends on the suspected cause. Plain X-ray identifies later-stage structural changes including joint space narrowing and fusion in ankylosing spondylitis. MRI — particularly with STIR sequences — identifies early inflammatory changes in the SIJ bone marrow (bone marrow oedema) that precede X-ray changes by years and are critical for early diagnosis of inflammatory arthropathy. Where inflammatory arthropathy is suspected, referral to a rheumatologist for blood tests including HLA-B27, CRP and ESR alongside imaging is appropriate. Arthritis Australia provides comprehensive patient information on ankylosing spondylitis and related conditions.
How can physiotherapy help?
For inflammatory sacroiliitis associated with ankylosing spondylitis or other spondyloarthropathies, physiotherapy is an evidence-based and essential component of management alongside medical treatment with anti-inflammatory medications and where indicated, biological therapies. The physiotherapy focus is on maintaining spinal and hip mobility, building the postural and core muscle strength that prevents the spinal stiffening and postural deformity that characterises advanced ankylosing spondylitis, and education on activity modification and self-management.
For mechanical sacroiliitis, the approach closely follows that for sacroiliac joint dysfunction — addressing the biomechanical factors that are overloading the joint, restoring normal force transfer through the pelvis, and building the muscular support system around the SIJ. Deep stabilising muscle rehabilitation — transversus abdominis, multifidus and pelvic floor — is central to improving the active stability of the sacroiliac joint and reducing the load on the passive ligamentous structures.
Sacroiliac belts provide useful short-term support by compressing the pelvis and improving force closure of the SIJ, particularly during the acute phase and in pregnancy-related presentations. Dry needling assists with pain management in the surrounding gluteal and lumbar musculature. Real time ultrasound guides deep stabilising muscle retraining. Clinical Pilates provides an excellent environment for progressive core and hip strengthening without the asymmetric loading that aggravates SIJ pain.
For patients with leg length discrepancy contributing to SIJ overload, heel raise orthotics may be recommended alongside physiotherapy. Postural and movement education — how to sit, stand, lift and roll in bed without aggravating the SIJ — is a practical and important component of management.
Our physiotherapists Bethany Kippen and Emma Cameron both have experience in SIJ conditions and pelvic pain management and are members of the Australian Physiotherapy Association.
To book or find out more, call us on 07 3706 3407 or book online below. We see patients from across Brisbane's southside including Tarragindi, Coorparoo, Holland Park, Greenslopes and Mt Gravatt.
Sacroiliitis refers specifically to inflammation of the sacroiliac joints — the two joints connecting the sacrum (the triangular bone at the base of the spine) to the ilium (the large wings of the pelvis). These joints bear significant load in standing and walking, transmitting forces between the spine and the lower limbs, and are stabilised by some of the strongest ligaments in the body.
Sacroiliitis is distinct from the broader term sacroiliac joint dysfunction (SIJD), which describes mechanical dysfunction of the SIJ without necessarily involving active inflammation. Sacroiliitis implies a specific inflammatory process within the joint — either from an inflammatory arthropathy, infection, or significant mechanical overload — and its management reflects this distinction. That said, in clinical and everyday usage the two terms are often used interchangeably, and many people presenting with SIJ pain have elements of both.
What causes sacroiliitis?
The most clinically significant cause is inflammatory arthropathy — systemic inflammatory conditions that cause joint inflammation as part of a broader disease process. Ankylosing spondylitis (now classified as axial spondyloarthritis) is the condition most strongly associated with sacroiliitis, characteristically producing bilateral SIJ inflammation that is often the earliest manifestation of the disease. Psoriatic arthritis, reactive arthritis, and inflammatory bowel disease-associated arthritis can also produce sacroiliitis. In these conditions, sacroiliitis is not a mechanical problem but a systemic one requiring medical management alongside physiotherapy.
Mechanical sacroiliitis — where the joint becomes inflamed from biomechanical stress rather than a systemic disease — is also well recognised. Pregnancy and the postnatal period, leg length discrepancy, scoliosis, previous spinal surgery, and sports with repetitive asymmetric loading are all associated with mechanically-driven SIJ inflammation. Pelvic girdle pain during and after pregnancy frequently has a significant sacroiliac component.
Infective sacroiliitis — bacterial infection of the SIJ — is rare but serious and requires urgent medical management rather than physiotherapy. It should be considered when sacroiliac pain is accompanied by fever, constitutional symptoms, or a history of intravenous drug use.
What are the symptoms?
Pain in the lower back, buttock and posterior pelvis is the hallmark symptom, typically unilateral (one side) in mechanical presentations and bilateral in inflammatory arthropathy. The pain may refer into the groin, thigh or even the calf, mimicking sciatica or hip pathology.
Stiffness is characteristic, particularly in the morning — in ankylosing spondylitis, morning stiffness lasting more than 45 minutes that improves with movement is a diagnostic hallmark. Pain is typically provoked by prolonged standing, walking, climbing stairs, rolling over in bed, and transitioning from sitting to standing.
How is sacroiliitis diagnosed?
Clinical assessment includes specific provocation tests for the SIJ — the FABER test, posterior pelvic pain provocation test (P4 test), Gaenslen's test and thigh thrust test — alongside evaluation of lumbar spine and hip mobility. The pattern of positive and negative tests helps differentiate SIJ from lumbar spine and hip pathology, though the three often coexist and all need to be assessed.
Imaging for sacroiliitis depends on the suspected cause. Plain X-ray identifies later-stage structural changes including joint space narrowing and fusion in ankylosing spondylitis. MRI — particularly with STIR sequences — identifies early inflammatory changes in the SIJ bone marrow (bone marrow oedema) that precede X-ray changes by years and are critical for early diagnosis of inflammatory arthropathy. Where inflammatory arthropathy is suspected, referral to a rheumatologist for blood tests including HLA-B27, CRP and ESR alongside imaging is appropriate. Arthritis Australia provides comprehensive patient information on ankylosing spondylitis and related conditions.
How can physiotherapy help?
For inflammatory sacroiliitis associated with ankylosing spondylitis or other spondyloarthropathies, physiotherapy is an evidence-based and essential component of management alongside medical treatment with anti-inflammatory medications and where indicated, biological therapies. The physiotherapy focus is on maintaining spinal and hip mobility, building the postural and core muscle strength that prevents the spinal stiffening and postural deformity that characterises advanced ankylosing spondylitis, and education on activity modification and self-management.
For mechanical sacroiliitis, the approach closely follows that for sacroiliac joint dysfunction — addressing the biomechanical factors that are overloading the joint, restoring normal force transfer through the pelvis, and building the muscular support system around the SIJ. Deep stabilising muscle rehabilitation — transversus abdominis, multifidus and pelvic floor — is central to improving the active stability of the sacroiliac joint and reducing the load on the passive ligamentous structures.
Sacroiliac belts provide useful short-term support by compressing the pelvis and improving force closure of the SIJ, particularly during the acute phase and in pregnancy-related presentations. Dry needling assists with pain management in the surrounding gluteal and lumbar musculature. Real time ultrasound guides deep stabilising muscle retraining. Clinical Pilates provides an excellent environment for progressive core and hip strengthening without the asymmetric loading that aggravates SIJ pain.
For patients with leg length discrepancy contributing to SIJ overload, heel raise orthotics may be recommended alongside physiotherapy. Postural and movement education — how to sit, stand, lift and roll in bed without aggravating the SIJ — is a practical and important component of management.
Our physiotherapists Bethany Kippen and Emma Cameron both have experience in SIJ conditions and pelvic pain management and are members of the Australian Physiotherapy Association.
To book or find out more, call us on 07 3706 3407 or book online below. We see patients from across Brisbane's southside including Tarragindi, Coorparoo, Holland Park, Greenslopes and Mt Gravatt.
