What Is Psoriatic Arthritis, and How Does It Affect the Spine?
Psoriatic arthritis is a type of inflammatory arthritis linked to the skin condition psoriasis. In some people it affects the spine and the sacroiliac joints at the base of the back, causing deep stiffness and pain that is often worse after rest. A standing whole-body scan can show how this inflammation changes your spinal alignment under real weight-bearing load.
Key takeaways
- Psoriatic arthritis can affect the spine, sacroiliac joints, and the points where tendons meet bone.
- Inflammatory back pain typically feels worst first thing in the morning and improves with movement.
- Lying-down scans can miss alignment shifts that only appear when you are standing and bearing weight.
- A standing EOS scan captures the full spine and pelvis in one low-radiation image, showing the real picture.
- Early imaging helps rheumatologists plan the right treatment sooner.
What is psoriatic arthritis?
Psoriatic arthritis is a chronic inflammatory condition that causes pain, swelling and stiffness in your joints. It develops in some people who already have the skin condition psoriasis, though joint symptoms occasionally appear before any skin changes do. Unlike osteoarthritis, which is caused by wear and tear, psoriatic arthritis is driven by an overactive immune system that attacks healthy joint tissue.
The condition can affect almost any joint, from fingers and toes to shoulders and knees. When it involves the spine and the sacroiliac joints connecting the spine to the pelvis, it is sometimes called psoriatic spondylitis. This axial involvement is more common than many people realise, and it can change the way your entire spine lines up.
What are the symptoms of psoriatic arthritis?
Psoriatic arthritis symptoms vary from person to person, but the most common ones include joint pain, swelling and morning stiffness that lasts more than 30 minutes. Symptoms often come and go in flares.
Some people also notice fatigue that feels out of proportion to their activity. If you experience sudden weakness, numbness in your legs, or any loss of bladder or bowel control, seek urgent medical attention from your GP, 111, or A&E straight away.
How does psoriatic arthritis affect the spine?
When psoriatic arthritis involves the spine, it typically targets the sacroiliac joints and the lower lumbar vertebrae. Inflammation at these sites, known as sacroiliitis, causes deep, aching back pain that is usually worse after sleeping or sitting still. Unlike mechanical back pain, it tends to improve with exercise rather than rest.
Over time, this inflammation can change the shape and movement of your spine. Bony growths called syndesmophytes may form along the edges of vertebrae, sometimes in an asymmetric pattern that is quite different from other forms of inflammatory arthritis. This asymmetry can shift your sagittal balance, the natural front-to-back alignment of the spine when you stand upright.
Your body is a connected chain from your feet to your head. If inflammation stiffens the lower spine and pelvis, the upper spine and hips will compensate. This means pain may show up in places quite far from the original problem. A scan of just the painful area might not show the full story.
If you have psoriasis and unexplained back stiffness, a standing full-spine image can show whether your alignment has changed.
Book a free video consultationWhy does a standing scan show more than a lying-down scan?
Most imaging, including standard X-rays, CT and MRI, is done while you lie down. In that position your muscles relax, your joints decompress, and gravity no longer pulls on your skeleton the way it does all day. The result is a picture of your bones and joints in a position you rarely actually use.
A standing EOS scan captures your entire spine and pelvis, from the base of the skull to the hips, while you stand naturally. Because your full body weight is passing through the skeleton, the image shows exactly how your joints line up under real-world load. If psoriatic arthritis has changed the shape of your sacroiliac joints or stiffened part of the lumbar spine, a standing image reveals how the rest of the chain is compensating.
Full weight-bearing image. Gravity loads the spine naturally, so the scan shows how your vertebrae, pelvis and hips actually align when you stand. It captures the whole chain in a single, low-radiation exposure, about 90% less radiation than a standard X-ray, around ten times less.
Unloaded image. Lying flat removes gravity. Joints decompress and muscles relax, which can mask asymmetries and alignment shifts caused by inflammatory stiffness. The scan may also only cover one region, missing the compensations happening elsewhere.
ScanAlign standing EOS imaging gives your rheumatologist or spinal specialist a complete picture of how psoriatic spondylitis is affecting your posture and alignment, not just the one joint that hurts.
How is psoriatic arthritis diagnosed?
Psoriatic arthritis diagnosis usually involves a combination of clinical examination, blood tests and imaging. A rheumatologist will look at your skin and nails, check your joints for swelling and tenderness, and order blood markers to rule out other types of inflammatory arthritis. There is no single definitive test, so diagnosis depends on the overall clinical picture.
Imaging plays an important role. Standard X-rays can show joint damage and bony changes, but they may miss early inflammation and cannot reveal how your whole spine and pelvis are lining up in the position where you actually feel pain. A standing scan adds the missing dimension of real-world weight bearing.
When MRI is the better tool. EOS shows bones, joints and alignment clearly. For soft tissue, discs, nerves or early inflammation inside the sacroiliac joint itself, MRI is usually the better choice. Your specialist may want both for a complete assessment.
What helps manage psoriatic arthritis in the spine?
Treatment is guided by your rheumatologist and may include disease-modifying drugs (often called DMARDs), biologics, physiotherapy and lifestyle changes such as regular low-impact exercise. ScanAlign is a diagnostic imaging clinic, not a treatment provider. Our role is to give you and your medical team a clear, accurate picture of where your alignment stands today, so treatment decisions are based on the best possible information.
If you are considering any form of spinal or joint intervention, accurate baseline alignment data helps your surgeon or specialist plan with confidence. You can book a standing spine scan without needing a GP referral.
Frequently asked questions
Yes. When psoriatic arthritis involves the spine and sacroiliac joints, it is called psoriatic spondylitis. It causes inflammatory back pain, stiffness and, over time, possible changes to spinal alignment.
It tends to be a deep, aching stiffness in the lower back or buttocks. It is usually worse after periods of rest, especially first thing in the morning, and improves with movement and gentle exercise.
Most people develop skin psoriasis first, but in some cases the joint symptoms appear before any noticeable skin or nail changes. A family history of psoriasis is also relevant.
An EOS scan captures your full spine and pelvis in one standing image, showing alignment under real weight-bearing load. It uses about 90% less radiation than a standard X-ray, around ten times less.
No. You can self-refer. The process starts with a free video consultation where a specialist radiographer discusses your symptoms and confirms whether a standing scan is appropriate for you.
Yes. The EOS system uses about 90% less radiation than a standard X-ray, around ten times less. This makes it one of the lowest-dose skeletal imaging options available.
ScanAlign is a private self-pay clinic. For current pricing and what is included, please visit the FAQs page on the website.
No single scan diagnoses psoriatic arthritis by itself. Diagnosis involves clinical examination, blood tests and often several types of imaging. An EOS scan shows bony alignment changes and joint damage, adding valuable information to the full clinical picture.
MRI is better at detecting early soft-tissue inflammation and bone marrow oedema inside the sacroiliac joints. EOS is better at showing whole-spine alignment under load. Your specialist may recommend both.
You stand still in the scanner for around 15 to 20 seconds while the image is taken. There is no enclosed tunnel and no loud noise. Comfortable clothing without metal fastenings is ideal.
See how your spine really lines up
If psoriatic arthritis is affecting your back or posture, a standing scan shows the full picture. Start with a free video consultation.
Book a free video consultationWritten by Abbas Dhami (Specialist Diagnostic Radiographer)
Sources
- National Psoriasis Foundation. "About Psoriatic Arthritis." psoriasis.org.
- Ritchlin CT, Colbert RA, Gladman DD. "Psoriatic Arthritis." New England Journal of Medicine, 2017; 376(10): 957-970.
- NHS. "Psoriatic arthritis." nhs.uk/conditions/psoriatic-arthritis.
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.