Deep in the back of your pelvis, you have a joint called the sacroiliac (SI) joint, which connects the bottom of your spine to your pelvis on each side. Problems with these joints are associated with up to 30% of lower back pain cases.1

Sacroiliac joint dysfunction is responsible for 15% to 30% of lower back pain cases

The sacroiliac joint(s) can become a source of pain back and leg pain when there is either too much or too little movement in the joints. Inflammation of the sacroiliac joint (sacroiliitis) can also produce pelvic pain and stiffness. Watch Sacroiliac Joint Dysfunction Video

This blog highlights what you need to know about your SI joints and how they can contribute to lower back pain.

What is a sacroiliac joint?

The SI joint is where the base of your spine (sacrum) connects to the butterfly-shaped group of bones in your pelvis.1

  • The joint surfaces are covered with cartilage, held together by a fibrous capsule, and surrounded by synovial fluid (lubricating joint fluid).2
  • Several ligaments surround the joint, providing strength and limiting its mobility.2

You have one of these joints on each side.1

Read more about Sacroiliac Joint Anatomy

What does the sacroiliac joint do?

The SI joints support the weight of your upper body. They act as shock absorbers during the transfer of loads from the trunk of your body into your pelvis and legs. They also support your range of motion when you bend or twist at your hips.3

These joints are sturdy, have minimal mobility, and can withstand tremendous pressure.1,3

How does the sacroiliac joint become painful?

SI joint pain occurs when there is malalignment or abnormal motion, such as too much or too little motion within the joint(s).3

These painful conditions may develop gradually over time or from an inciting event:

  • External trauma. High energy impacts, such as from a motor vehicle accident or a fall, may fracture or cause malalignment of the SI joint. Traumatic injuries may also overstretch (strain) the joint’s ligaments, causing pain.2,3
  • Repetitive stress. Stressing the joint over time, such as daily jogging or weight lifting, may cause the SI joint and/or its surrounding ligaments to become painful.2,3,4
  • Arthritis. Degenerative arthritis (osteoarthritis) or inflammatory arthritis (reactive or psoriatic arthritis) of the SI joint may cause lower back pain.3
  • Pregnancy. The SI joint’s ligaments become relaxed and loose during pregnancy, making the joint more mobile than usual. Increased body weight and added pressure in the abdomen and lower back increase loads on the SI joints and may cause lower back pain in up to 90% of pregnant women.2,5

Less common causes of SI joint pain include:

  • Infections3
  • Scoliosis (abnormal sideways curvature of the spine)3
  • Discrepancy in leg length3
  • Ankylosing spondylitis (chronic, multisystem inflammatory disorder primarily involving the sacroiliac joints and the skeleton)

    See Ankylosing Spondylitis

Carrying excessive weight and/or leading a sedentary lifestyle are contributing factors to SI joint pain.3

What does sacroiliac joint pain feel like?

Problems with your SI joint can be experienced with a wide range of symptoms, for example:

  • A sharp, stabbing, and/or shooting pain may be felt directly over your affected joint – on the right or left side of the back of your hip. Alternatively, you may feel more of a persistent, dull ache in that area.3
  • The pain is usually localized to the lower back and/or over the buttock.3,6 The pain may also extend down the back of your thigh, but typically does not extend below the knee.3
  • Certain positions or activities may cause your pain to flare up, such as going from standing to sitting, climbing stairs, or lying on the affected side.3

In addition to lower back pain, problems in the SI joint may mimic radicular (spinal nerve-root related) pain,3 commonly referred to as sciatica.

Read more about Sacroiliac Joint Dysfunction Symptoms and Causes

How is sacroiliac joint pain treated?

The treatment of SI joint pain usually involves a multidisciplinary approach and may include a primary care provider, a physical therapist, and an orthopedic surgeon, among others.3

SI joint pain treatments typically include3:

If the pain is severe, assistive devices, such as walkers may be used. Sacroiliac belts may be worn temporarily for short periods in case of pelvic instability. Minimally invasive treatments, such as radiofrequency ablation (creating heat lesions on nerves to stop them from transmitting pain) may be considered in severe SI joint dysfunction. Rarely, SI fusion surgery may be recommended.3

See Surgical Treatment for Sacroiliac Joint Pain

If you suspect your SI joint(s) to be a cause of your lower back pain, consult your doctor for a medical examination. A doctor can conduct specific clinical tests, rule out serious underlying conditions, such as tumors or infections, and formulate an effective treatment plan for your SI joint pain.

See Accurate Diagnosis of Sacroiliac Joint Dysfunction

Learn more:

Treatment Options for Sacroiliac Joint Dysfunction

Slideshow: Sacroiliac Joint Exercises for Sciatic Pain Relief

  • Referrence
    • 1.Rashbaum RF, Ohnmeiss DD, Lindley EM, Kitchel SH, Patel VV. Sacroiliac Joint Pain and Its Treatment. Clinical Spine Surgery. 2016;29(2):42-48. doi:10.1097/bsd.0000000000000359
    • 2.Cohen SP, Chen Y, Neufeld NJ. Sacroiliac joint pain: a comprehensive review of epidemiology, diagnosis and treatment. Expert Review of Neurotherapeutics. 2013;13(1):99-116. doi:10.1586/ern.12.148
    • 3.Raj MA, Varacallo M. Sacroiliac (SI) Joint Pain. [Updated 2019 May 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470299/
    • 4.Thawrani DP, Agabegi SS, Asghar F. Diagnosing Sacroiliac Joint Pain. Journal of the American Academy of Orthopaedic Surgeons. 2019;27(3):85-93. doi:10.5435/jaaos-d-17-00132
    • 5.Filipec M, Jadanec M, Kostovic-Srzentic M, van der Vaart H, Matijevic R. Incidence, pain, and mobility assessment of pregnant women with sacroiliac dysfunction. International Journal of Gynecology & Obstetrics. 2018;142(3):283-287. doi:10.1002/ijgo.12560
    • 6.Polly DW, Cher D. Ignoring the sacroiliac joint in chronic low back pain is costly [published correction appears in Clinicoecon Outcomes Res. 2016;8:349]. Clinicoecon Outcomes Res. 2016;8:23–31. Published 2016 Jan 21. doi:10.2147/CEOR.S97345
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