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What is the sacroiliac joint?

The sacroiliac (SI) joints are the two places where your hip bones, or ilium, attach to the left and right side of the sacrum, a triangular bone in the center of your lower back between the spine and the tailbone. The SI joints’ main function is to carry the weight of your upper body when you stand or walk and shift that load to your legs via your hips.

 

What is difference between sacroiliac joint pain and sacroiliitis?

Both sacroiliac joint pain and sacroiliitis involve the SI joint, where the spine connects to the pelvis. 

However, the two differ in their causes and characteristics:

  • SI joint pain is the broad term that includes any pain stemming from, as you would assume, the SI joint. Unlike sacroiliitis, this form of pain is not always inflammatory. Non-inflammatory causes of SI joint pain include misalignment, stiffness, or movement problems related to overuse, poor posture, muscle imbalances, or even pregnancy. 

  • Sacroiliitis is a type of SI joint pain where the joint becomes inflamed. This inflammation is usually triggered by an underlying condition, such as osteoarthritis, an autoimmune disease like ankylosing spondylitis, infection, or trauma. Sacroiliitis generally causes pain in the lower back, buttocks, or hips. The pain might get worse with certain movements, like standing up from sitting, or climbing stairs. Treatment often involves addressing inflammation, sometimes with the help of a rheumatologist. An orthopedic specialist can help you determine if your SI joint pain is due to sacroiliitis and refer you to an appropriate specialist.

What does SI joint pain feel like?

SI joint pain is centered in the pelvis and can radiate from the points where the bones attach to affect the lower back, buttocks, and legs. Less commonly, it can affect the groin and feet.

Both SI joints can ache simultaneously, but it's more common for SI joint pain to occur on one side, also known as “unilateral" SI joint pain.

Sacroiliac joint pain symptoms can resemble symptoms of several other conditions, such as sciatica, lumbago, or disc problems in the spine. Common signs of pain in the sacroiliac joint include:

  • Pain that gets worse after standing, sleeping, or sitting for a long time
  • Pain that gets worse with activity, like running or climbing stairs
  • Morning stiffness in the hips or lower back
  • Instability in the hips and lower back

How long does sacroiliac joint pain last?

Depending on the cause, SI joint pain can be chronic (persistent) or acute (sudden and/or temporary). Acute SI joint pain may be the result of an injury, while chronic pain often has other causes. Acute pain may go away in a matter of days or weeks. Chronic pain in the sacroiliac joint may not improve unless you address its root cause. 

What causes sacroiliac joint pain?

Common causes of SI joint pain include:

  • Arthritis: Both osteoarthritis and ankylosing spondylitis, an inflammatory autoimmune disease affecting the SI joint, can lead to sacroiliitis. 

  • Gait problems: Conditions or habits that affect how you walk can cause you to load your SI joint unevenly or inappropriately. For example, scoliosis, different length legs, or injuries to structures that affect gait—such as Achilles tendon ruptures or ACL injuries—may cause you to walk differently and lead to sacroiliac joint pain. 

  • Injury: Traumatic injuries such as falls can cause pain in the SI joint. 

  • Other conditions: Diseases that cause systemic inflammation can result in sacroiliitis and subsequent SI joint pain. 

  • Pregnancy: During pregnancy, the joints in the hips, including the SI joints, change to prepare for childbirth. Pregnancy also causes changes in your gait, which can provoke SI joint pain.

It's possible for the SI joint to get infected, causing inflammation and SI joint pain, but it's rare.

What aggravates sacroiliac joint pain?

Anything that causes you to put too much stress on the SI joint can aggravate sacroiliac joint pain, including standing on one leg, poor posture, repetitive motions, contact sports, standing or sitting for a long time, and high-impact exercise like jumping or plyometrics. 

What is the treatment for sacroiliac joint pain?

Sacroiliac joint pain treatment is usually treated with non-invasive, non-surgical methods. In the short term, you may need to take anti-inflammatory drugs like ibuprofen or receive cortisone injections to reduce inflammation in the SI joint. 

In the long term, physical therapy is the most common treatment for SI joint pain. Strengthening the muscles and connective tissue in the hips and back can reduce stress on the sacroiliac joint and relieve pain. A physical therapist can also help you identify issues with your posture and biomechanics (the way you move) that may contribute to SI joint pain.

In severe cases that persist after conservative treatments, surgery to fuse the SI joint may be a solution.

Sacroiliac joint pain exercises

Your physical therapist can prescribe specific exercises for sacroiliac joint pain. Generally, sacroiliac joint pain responds to stretches that increase mobility in the hips and lower back. Exercises that strengthen the structures supporting the pelvis and back can also help:

  • Mobility: Stretches for sacroiliac joint pain include knee-to-chest, quad stretches, hamstring stretches, and hip abductor stretches. 

  • Strengthening: Exercises for sacroiliac joint pain include glute bridges, bird dogs, hip and resistance abductions, squats, lunges, and strengthening exercises for the lower abdominals.

FAQs about SI joint pain

It depends on the cause of your SI joint pain. Acute pain—like that caused by a traumatic injury—may go away on its own as the area heals or with conservative treatment. For chronic pain in the sacroiliac joint, the best treatment usually involves physical therapy to repair asymmetries, combined with reducing or eliminating habits that stress the joint. If your SI joint pain is caused by another condition, such as arthritis, you'll need to treat the underlying condition.

Side sleeping is the most common sleeping position, but it can put pressure on the SI joint. 

Sleeping on your back with a pillow under your knees may be a better choice to alleviate sacroiliac joint pain. If you need to sleep on your side to be comfortable, try putting a pillow between your legs to reduce the pressure and keep your legs in a more neutral position.

Prolonged sitting can aggravate SI joint pain. Taking frequent breaks to stretch or move around can help with symptoms of SI joint pain. You may also want to change sitting position frequently to change the way your weight is distributed on your hips and buttocks.

Good sitting posture can also help. A straight (but not tense) back with relaxed shoulders and wide knees can help reduce the strain on your hips. Keep your knees at or below hip level, with your feet flat on the floor. An adjustable-height chair can help you achieve the right position. Evaluate whether you sit with your weight equally distributed on both buttocks, or if you tend to load one side more than the other.

Walking is a low-impact alternative to running and can help relieve SI joint pain by strengthening the legs, glutes, and lower back. Pay attention to your posture and gait as you walk and look for irregularities that may put unnecessary stress on the SI joint, such as leaning to one side or uneven stride length. 

People with sacroiliac joint pain should avoid high-impact activities, sitting or standing in one position for long periods, repetitive motions, and positions that load the hips unevenly. 

Depending on the severity and cause of the SI joint pain, it may go away on its own with rest and time. When it results from another condition or activity, it probably won't go away until you address the root cause. Extreme cases may require surgery to fuse the SI joint.

Many cases of sacroiliac joint pain can be successfully treated with conservative methods like physical therapy and anti-inflammatory medications. In cases that result from another condition, such as osteoarthritis, curing SI joint pain may depend on whether the underlying condition can be cured.

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