Sacroiliitis – what is it and why does it hurt?
The sacroiliac joints, also called the SI joints, function as shock absorbers between the upper body and the legs. When these joints become inflamed, mobility is affected and pain occurs—this is called sacroiliitis. It can feel like ordinary back pain, which means sacroiliitis is sometimes mistaken for other conditions such as disc problems or sciatica. The difference is that the pain is often deeper and more on one side of the lower back or in the buttock area.
Common symptoms of sacroiliitis
Most people with sacroiliitis seek care for pain in the lower back or over one buttock. The pain can sometimes radiate down toward the thigh or groin, which can make it difficult to determine where the problem actually originates.
Typical signs of sacroiliitis include:
- Pain in the lower back, pelvis, or buttock
- Stiffness in the morning or after rest
- Worsening pain with prolonged sitting or standing
- Discomfort when climbing stairs, running, or standing up
- Aching pain that may radiate to the thigh or groin
In inflammatory causes, such as rheumatoid arthritis, the pain may also develop gradually, feel worse at night, and be accompanied by fatigue.
Common causes of inflammation in the SI joint
Sacroiliitis can occur for several different reasons. In many cases, it involves a combination of strain and sensitivity in the joint. A common cause is overuse, for example after repetitive movements, heavy training, or prolonged sitting. Pregnancy is also a known factor, as the pelvis changes and is loaded differently. Injuries, such as falls or blows to the back, can also trigger symptoms. In some individuals, sacroiliitis is due to an inflammatory disease, such as axial spondyloarthritis (previously called Bechterew’s disease). In these cases, the inflammation is more long-lasting and requires specific treatment. In more rare cases, infection may be the underlying cause.
When should you seek care for SI joint pain?
Seek medical care if you have had pain in the lower back or pelvis for several weeks without improvement. This is especially important if the pain affects your sleep, causes morning stiffness, or interferes with your daily life. You should seek urgent care if you experience severe pain after an injury, fever combined with back pain, or if you notice numbness, weakness in the legs, or problems with bladder or bowel function.
Diagnosis of sacroiliitis – how is it done?
The evaluation usually begins with a clinical examination where you describe your symptoms and answer questions about how the pain feels and when it occurs. The doctor performs a physical exam, testing movements that stress the SI joint. If needed, this may be supplemented with blood tests or imaging, such as X-ray or MRI of the hip and pelvis, especially if an inflammatory disease is suspected.
Treatment of sacroiliitis – what helps relieve the pain?
Treatment is tailored to the cause but focuses on reducing inflammation and improving mobility. In most cases, a combination of movement and targeted exercise provides the best long-term results. Physiotherapy is often a key component and helps strengthen the muscles around the pelvis and back. Pain-relieving and anti-inflammatory medications may be used when needed. If sacroiliitis is linked to a rheumatic disease, more specific medical treatment may be required. In some cases, an injection into the joint may be considered to reduce inflammation.
Self-care for sacroiliitis – what can you do yourself?
Keeping your body moving is one of the most important ways to reduce SI joint symptoms. Light exercise such as walking, mobility exercises, and stability training can make a big difference. Try to avoid sitting still in the same position for long periods and vary your activity throughout the day. Heat, such as a wheat bag or a warm shower, can also help relieve pain for many people.
Prognosis – how long does sacroiliitis last?
Most people improve with the right treatment and adjusted activity. For some, symptoms resolve within a few weeks, while others may experience recurring problems. If sacroiliitis is caused by an inflammatory disease, it is important to receive the correct diagnosis early. With proper treatment, symptoms can be reduced and quality of life improved in the long term.