What Is Sacroiliac Joint Pain? The Condition Often Mistaken for Back Pain

A stubborn pain where the low back meets the hip, often felt on one side — and a picture that is taken for a “herniated disc” or “sciatica” and never quite resolves. Behind it there is frequently an overlooked source: the sacroiliac joint. In this article we look at what sacroiliac joint pain is, why it is so often confused with other back problems, why its diagnosis calls for care, and the role physiotherapy plays in this picture.

What is the sacroiliac (SI) joint, and where is it?

The sacroiliac joint is where the sacrum — the triangular bone above the tailbone, at the very bottom of the spine — meets the pelvis (the ilium). There is one on each side of the body, just below your lower back, on the inner side of the hip prominences. It is a strong, minimally-moving joint supported by strong ligaments. Its job is to transfer the load from the upper body down to the legs and to balance the forces generated while walking. In other words, it is a “load-transfer and balance” joint far more than a “movement” joint.

What is sacroiliac joint pain?

Sacroiliac joint pain is pain arising from this joint or from the structures around it. The joint can become painful through excessive or uneven loading, a trauma, or the supporting muscles not working enough. There is an important distinction here: sometimes people speak of “sacroiliac dysfunction”, meaning a disturbance in how the joint moves; but such a movement disturbance does not always cause pain. That is why what really matters is not a theoretical “dysfunction” in the joint, but the pain the person actually experiences and how it affects their function.

What are the symptoms?

Sacroiliac joint pain has a location of its own. The pain is most often felt at the junction of the lower back and the hip, frequently on one side, and usually not right in the midline. It may spread to the buttock, the groin, and sometimes the back of the thigh; but it mostly does not travel below the knee. Prolonged sitting, standing, climbing stairs, standing on one leg, or turning over in bed can worsen the pain. A person can often point to the painful spot with a single finger, just above the buttock — a typical clue for the sacroiliac joint.

How is it different from a herniated disc and sciatica?

The conditions sacroiliac joint pain is most confused with are a herniated disc and sciatica — because all of them can produce symptoms in the low-back–hip–leg region. But there are important differences. In disc-related sciatica the pain radiates along a nerve path below the knee, sometimes as far as the foot, and is often accompanied by nerve symptoms such as numbness and tingling. Sacroiliac joint pain, by contrast, concentrates more at the low-back–hip junction and over the joint, usually does not travel below the knee, and typical nerve symptoms are not to the fore. These distinctions are not always clear-cut and the pictures can coexist; that is why a definite distinction becomes clear through a careful assessment. For nerve-related causes of leg-radiating pain, you can read our article What Is Sciatica?.

Why does it happen?

Sacroiliac joint pain can have more than one cause. One of the most familiar is pregnancy and childbirth; during this period the hormones released loosen the pelvic ligaments and make the joint more prone to pain. Beyond this, a trauma such as a fall or a blow, a leg length difference or asymmetric loading, weak or imbalanced work by the supporting muscles, and prolonged inactivity can all contribute to the picture. Some inflammatory rheumatological conditions can also affect the sacroiliac joint; this is why assessment matters, especially with a young age and persistent symptoms.

Why does the diagnosis call for care?

We should be honest here: diagnosing sacroiliac joint pain is harder than it looks. No single examination test or single imaging study proves, on its own, that the joint is definitely the source of the pain. Instead, the physiotherapist uses several different provocation tests together and interprets them as a whole, alongside the person’s history and other findings. Several of these tests being positive together, and the symptoms not being attributable to another source, markedly strengthen the likelihood of the sacroiliac joint. In other words, the diagnosis rests not on a single test but on careful clinical reasoning — which is exactly why a good assessment matters.

How is it assessed in physiotherapy?

The aim in physiotherapy is to understand whether the pain truly arises from the sacroiliac joint, and to distinguish the picture from similar-looking conditions such as a herniated disc, sciatica or hip problems. The assessment examines the location and behaviour of the pain (where it is, what worsens it, where it spreads), a set of provocation tests, and the strength and balance of the muscles around the pelvis and hip. This whole-picture assessment forms the basis both for the right direction and for an individualised programme.

How is it treated?

At the centre of physiotherapy for sacroiliac joint pain is the retraining of the muscles that support the joint. The sacroiliac joint stays stable through the muscles around it (the hip, core and pelvic muscles) gripping and compressing it almost like a belt. The pain is often linked to these muscles not working enough or evenly. This is why the foundation of treatment is a stabilisation programme that strengthens these muscles and brings them to support the joint better. This can be accompanied by manual therapy that provides relief during painful periods, flexibility work for tightened areas, and — where needed — a pelvic belt that supports the joint from the outside. The aim is not a one-off intervention like “putting the joint back”, but permanently strengthening the support surrounding it. For a general overview of the lower back and the treatment approach, you can see the Lower Back Pain page.

How are exercises chosen?

In sacroiliac joint pain, exercise is chosen according to the person’s symptoms, their muscle strength and balance, and what they can tolerate. The general tendency is to place weight on stabilisation work that strengthens the hip, trunk and the area around the pelvis and increases the joint’s support. Over time, work that gradually increases the joint’s load-bearing capacity is also added to the programme — because this joint is one that needs to be strongly supported and prepared for load, not protected. Yet even this general framework is tailored to the person; the programme rests on assessment and is updated according to the person’s response.

Pregnancy and sacroiliac joint pain

Pregnancy and the postpartum period are among the most common settings for sacroiliac joint pain. The hormones released in pregnancy loosen the pelvic ligaments in preparation for birth; this can make the sacroiliac joint more mobile and more prone to pain. During this period the pain can usually be managed with suitable exercises that strengthen the muscles supporting the pelvis and, where needed, a pelvic belt. It is important that the programme be planned carefully and appropriately for the pregnancy or postpartum period.

What is recovery like?

The course of sacroiliac joint pain is favourable for most people. The effect of a suitable physiotherapy programme is often felt within a few weeks; but truly strengthening the support surrounding the joint is a gradual process that, depending on the person, can take a few months. What matters is that the process is carried out with the aim of permanently strengthening the surrounding support, not with the aim of “fixing the joint once”. When managed well, many people who experience sacroiliac joint pain return to a pain-free and active life.

When is an assessment needed?

If you have pain at the low-back–hip junction that has not settled for a few weeks, is steadily increasing, or is restricting your daily life, a physiotherapy assessment will both clarify the source of the pain and offer you a suitable programme. Persistent symptoms that begin at a young age, are notably worse at night, or come with long-lasting morning stiffness; or pain accompanied by marked weakness in the leg or a change in bladder or bowel control, call for an earlier and careful assessment. Such symptoms are uncommon, but assessing them in good time is important.

References

• Sacroiliac Joint Dysfunction — StatPearls / NCBI
• Diagnosis and Treatment of Sacroiliac Joint Pain — AAFP
• The Sacroiliac Joint: Diagnosis and Provocation Tests — Laslett / JOSPT
• Sacroiliac Joint Pain: Stabilisation and Exercise — Physiopedia