Sacroillitis - When to suspect and what should I do?

Introduction

Sacroiliitis is an inflammatory condition of one or both of the sacroiliac joints and is often linked to diseases like ankylosing spondylitis and other spondyloarthropathies. As we have touched on before with the other articles in this series it presents a challenge to diagnose as often presents as low back pain and sometimes with pain into the lower limbs also. This article outlines key assessment points, treatment options, evidence supporting these methods, and when to refer patients to a rheumatology confidently! (hopefully!)

Key Assessment Points

Patient History and Symptoms:

• Pain Characteristics: Patients typically describe pain in the lower back, buttocks, or upper legs. The pain is often bilateral but can be unilateral and may worsen with prolonged standing or weight-bearing activities. The pain is often below the iliac crests when asked to point to it but equally, as Sacroiliitis is often an early precursor to ankylosing spondylitis, consider symptoms of inflammatory type back pain
• Onset and Duration: The pain is usually insidious and chronic, often worsening at night or early morning, often no real mechanical pattern to the pain and look our for those inflammatory type signs and symptoms!
• Associated Symptoms: Look for signs of systemic inflammation, such as morning stiffness lasting more than 30 minutes, which may indicate an underlying inflammatory condition like ankylosing spondylitis.
• SPADE Tool - really useful for looking into inflammatory signs and symptoms especially if you are suspecting ankylosing spondylitis then the SPADE TOOL page on what is classed as inflammatory back pain is particularly good!

Physical Examination:

This isn't going to give you a lot of clues and doesn't really differentiate between SI joint pain and Sacroiliitis other than to tell you that it is more likely to be the SI joints involved in the pain rather than a lumbar structure or hip pain.

• Palpation: Tenderness over the sacroiliac joints but equally don't rule out based on this - could be more generalised pain around this area due to the inflammatory nature
• Provocative Tests: Ah, the special tests! FABER (Flexion, ABduction, and External Rotation) test, Gaenslen’s test, and sacral thrust test. These tests can help reproduce pain and localise the issue to the sacroiliac joints. However, as with sacroiliac joint pain, most of these test have limited diagnostic value when we look at the literature, and again I would do a cluster of them to really be sure it's sacroiliac joint pain.

Imaging:

Generally quite useful especially if the patient presents with more of an inflammatory presentation as they will differentiate between SI joint pain/dysfunction (generally normal imaging), lumbar spine cause (SIJ imaging will be generally normal) and sacroiliitis.

• X-ray: Initial imaging to detect joint space narrowing or sclerosis, particularly in chronic cases
• MRI: Preferred for detecting early sacroiliitis, as it can reveal bone marrow oedema, an early sign of inflammation.

Laboratory Tests:

• Inflammatory Markers: Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to help support the diagnosis of an inflammatory process.
• HLA-B27 Testing: Especially relevant if ankylosing spondylitis or another spondyloarthropathy is suspected

Key Treatment

Non-Pharmacological Interventions:

• Physiotherapy: Emphasise exercises that improve flexibility and strengthen the muscles around the sacroiliac joint. Core exercises can be particularly beneficial. A systematic review highlighted that tailored physiotherapy significantly reduces pain and improves function in patients with sacroiliitis
• Lifestyle Modifications: Weight management as in gait the SI joints help a lot with the weightbearing aspect but equally looking at optimising activity. What does the patient like doing? If they are generally active then looking at when their pain occurs. Can we look at different forms of activity that may be more offloading such as swimming? Don't forget this is a long term condition and therefore management like 'stopping anything that causes pain' isn't going to be helpful!

Pharmacological Interventions:

• NSAIDs: Non-steroidal anti-inflammatory drugs are the first line of pharmacological treatment to reduce inflammation and pain. Also can be used as a diagnostic - if significantly help (and when combined with other flags on the SPADE tool) then provide even more evidence for an inflammatory type presentation. Studies have consistently shown that NSAIDs are effective in reducing pain and inflammation in patients with sacroiliitis, particularly in those with an underlying inflammatory condition.
• Corticosteroids: Intra-articular injections of corticosteroids may be considered. These injections provide localised anti-inflammatory effects. Clinical studies indicate that corticosteroid injections can provide significant pain relief in patients with sacroiliitis, although the effects may be temporary
• Biologic Agents: For patients with sacroiliitis associated with ankylosing spondylitis or other spondyloarthropathies, biologics like TNF inhibitors can be effective. Randomized controlled trials (RCTs) have demonstrated the efficacy of TNF inhibitors in reducing symptoms and improving quality of life in patients with ankylosing spondylitis and associated sacroiliitis. This would be something I would be vague about with patients and leave to a Rheumatology decision - mentioning that Rheumatology have options and are the experts is good and it's also good to have an awareness of what can be offered!

Surgical Interventions:

• Guided Nerve Block: Just like it's the gold standard in identifying sacroiliac joint pain it can also be effective at controlling pain from sacroiliitis. However it has been shown to be less effective in this population due to the fact you are not 'treating' the underlying inflammatory cause
• Joint Fusion: In cases of severe pain unresponsive to conservative measures, sacroiliac joint fusion may be considered. However, this is typically a last resort.

Rheumatology Intervention and When to Refer

Referral Indicators:

• Chronic Pain: If the patient’s pain persists despite initial treatment efforts, referral to a rheumatologist is recommended, especially if that pain is around the sacroiliac joints and presents as more inflammatory in nature
• Suspected Systemic Disease: Patients presenting with signs of systemic involvement + sacroiliac pain (e.g., psoriasis, inflammatory bowel disease, or uveitis) should be referred for management. These patients will often be under Rheumatology
• Positive HLA-B27 and Imaging Findings: When diagnostic imaging and HLA-B27 testing are positive - bring in the experts!
• Positive SPADE Tool!! I will keep banging on about this, as it is really useful! If you get a positive result on the spade tool after inputting everything - definitely refer on. It's really good at making you consider an inflammatory presentation another good tool to consider an inflammatory presentation is the SCREEND'EM tool both will help you rule in/out inflammatory symptoms and strengthen your reasoning behind your referral.

If in doubt ask!!! GPs, colleagues or even advice and guidance from Rheumatology will be your friends here. Ask for advice and discuss cases. Patients rarely fit into a neat box of one condition!

Key Take-Aways

• Early diagnosis - suspect it, then look for the signs! If it doesn't fit into a mechanical pattern then don't make it fit. Consider an inflammatory cause and refer for the appropriate testing. I would start with some bloods and an x-ray if you're thinking inflammatory. If you're on the fence then consider some bloods and a review after some conservative management as this will help rule out and guide you. Early diagnosis does not mean image and test everyone with SI joint pain. It means consideration of the differentials and a clear assessment.
• Use of decision aids - use the SPADE tool and SCREEND'EM tools to help your reasoning of something inflammatory. Don't use them to replace your clinical reasoning ever, but especially in sacroillitis - reason? Often it's an early symptom. Consider the points on diagnosis above and use these as a guide. If they're positive, however, you should definitely be looking at a referral to Rheumatology. Consider something like an early inflammatory pathway if available.

References and Further Reading