Lower back and hip
Sacroiliitis inflames the sacroiliac joints and has several possible causes
Sacroiliitis means inflammation of one or both sacroiliac joints, and it is one of the recognized causes of low back pain [1]. Causes include inflammatory disease, injury or strain, age-related wear, and, rarely, infection [1][2].
Key points
- Sacroiliitis is inflammation of one or both sacroiliac joints, and it can seriously lower quality of life [1].
- Causes include inflammatory disease such as axial spondyloarthritis, injury or repeated strain, age-related wear, and, rarely, infection [1][2].
- In pregnancy or after delivery, fever with lower back or buttock pain should raise the possibility of infection in the joint, and no fever does not rule it out [2].
- MRI is often used in diagnosis, but swelling in the bone can also come from conditions that mimic sacroiliitis [3].
- Ankylosing spondylitis has no cure, but treatment can relieve symptoms and help delay progression [4][5].
Sacroiliitis causes low back pain and has several possible origins
Sacroiliitis is inflammation of one or both sacroiliac joints. It can lead to severe disability and a clear drop in quality of life [1]. It is reported in up to 25% of patients with low back pain [1].
Pain location varies by cause. In infectious sacroiliitis, pain was constant and most often felt in the buttock or the lower limb [2]. In ankylosing spondylitis, the most common symptom is lower back or hip pain with stiffness [5].
| Cause | What it looks like |
|---|---|
| Inflammatory | Linked to spondyloarthropathies and rheumatoid arthritis [1] |
| Mechanical or injury | Direct blows or repeated stress on the joint [1] |
| Age-related wear | Degenerative changes that bring localized pain [1] |
| Infection | Rare, about 1 to 2% of septic arthritis cases [2] |
Sacroiliitis is often underdiagnosed or given a nonspecific diagnosis, which can lead to ineffective treatment [1].
When to get care
Infectious sacroiliitis often brings fever with buttock or low back pain
Infection of the sacroiliac joint is rare, but pregnancy and the weeks after delivery have been linked to it [2]. Doctors are advised to consider this diagnosis for fever with lower back or buttock pain during pregnancy or after delivery [2].
In a review of reported cases, fever of 38.0°C or higher was present in over 75% of people [2]. The absence of fever does not rule the diagnosis out [2].
Diagnosis is often delayed. In the reviewed cases, the median time to diagnosis was 12.5 days [2]. MRI is the imaging test of choice, and it was abnormal in every case where it was done [2].
Treatment relies on antibiotics, sometimes combined with surgery, and outcomes are generally favorable [2]. Surgery was needed in 25% of the people in the reviewed cases [2].
If you think you may have a medical emergency in the United States, call 911 or go to the nearest emergency room.
Axial spondyloarthritis is one inflammatory cause of sacroiliitis
Ankylosing spondylitis is a long-term condition in which the spine and other areas of the body become inflamed [4]. It is a type of axial spondyloarthritis, and changes to the spine show up on an X-ray [4]. A similar condition, non-radiographic axial spondyloarthritis, shows no X-ray changes but can sometimes be seen on MRI [4].
Most people develop symptoms before age 45, though some start as children or teens [5]. Symptoms tend to develop gradually over months or years and may come and go [4].
- Pain that gets worse with rest or inactivity, including in the middle of the night, and usually improves with movement and exercise [5].
- Flares of symptoms that alternate with periods of remission [5].
- Pain, stiffness, and inflammation in other joints such as the ribs, shoulders, knees, or feet [5].
- Trouble taking deep breaths when the joints connecting the ribs are affected [5].
- Vision changes and eye pain from uveitis, which is inflammation of the eye [5].
- Abdominal pain and loose bowel movements [5].
Family history raises the risk, and so do Crohn's disease, ulcerative colitis, and psoriasis [5]. The HLA-B27 gene increases risk, but many people carry it and never develop the disease [5].
MRI helps doctors diagnose sacroiliitis but can mislead without context
If you have persistent symptoms of ankylosing spondylitis, a primary care doctor can refer you to a rheumatologist, a specialist in muscle and joint conditions [4]. Further tests may include blood tests and imaging [4].
MRI of the sacroiliac joints is often used to look for early inflammation and for structural changes [3]. Swelling in the bone marrow beneath the joint surface is an early sign of sacroiliitis, but it also occurs in many other conditions [3].
- Normal variations in joint anatomy can come with swelling that is not caused by inflammation [3].
- Pregnancy-related changes and other strain-related conditions can mimic sacroiliitis [3].
- Strain-related swelling is most common in the front part of the joint, while spondyloarthritis changes are more widespread [3].
- Erosions, a kind of structural damage, are more specific to axial spondyloarthritis [3].
Misdiagnosis can lead to inappropriate treatment [3]. A newer MRI method that measures water movement without contrast dye showed promise for separating active from inactive sacroiliitis, but the authors say it needs confirmation in further studies [6].
Treatment for sacroiliitis depends on the underlying cause
For ankylosing spondylitis, there is no cure and damage cannot be reversed, but treatment can relieve symptoms and help delay progression [4]. Care often combines exercise, physical therapy, and occupational therapy to improve mobility and posture [5]. Medicines can help manage pain and control inflammation [4][5]. These include painkillers, anti-TNF medication, and other biological therapy [4].
Surgery is sometimes needed for badly damaged joints or severe bends in the spine, but this is uncommon [4]. With treatment, most people with ankylosing spondylitis can have productive lives [5].
For sacroiliac joint pain from other causes, medicines, physical therapy, radiofrequency ablation, and joint fusion do not completely relieve pain for everyone [1]. Corticosteroid injections are widely recognized as the standard of care [1]. A small review compared them with platelet-rich plasma (PRP), a blood-derived product rich in growth factors [1].
| Point | Corticosteroid | PRP |
|---|---|---|
| Timing of relief | Faster, within 2 to 4 weeks [1] | Longer lasting, from week 8 up to 6 months [1] |
| Extra treatment needed | More often [1] | Less often [1] |
| Safety | Prolonged use is tied to osteoporosis, high blood pressure, and diabetes [1] | No significant adverse effects reported [1] |
Limits of the evidence
The authors say larger studies with longer follow-up are needed to understand the benefits and limits of both injections [1].
Sources
- Efficacy of Platelet-Rich Plasma Injections Versus Corticosteroid Injections in the Management of Chronic Low Back Pain Secondary to Sacroiliitis Pain research & management
- [Infectious sacroiliitis during pregnancy and the postpartum period: A case report and literature review] La Revue de medecine interne
- MRI sacroiliitis mimics Current opinion in rheumatology
- Ankylosing spondylitis nhs.uk
- Ankylosing Spondylitis Symptoms & Risk Factors niams.nih.gov
- Diagnostic performance of intravoxel incoherent motion imaging in evaluating sacroiliitis activity in axial spondyloarthritis: a meta-analysis The British journal of radiology
Not medical advice. This page is general education written from the sources above. It cannot diagnose a condition or replace a licensed clinician who knows your history. If you may be having an emergency, call your local emergency number or go to the nearest emergency department.