Sacroiliac (SI) Joint Dysfunction

Overview

what it is and why it matters

The sacroiliac (SI) joints are two paired joints at the back of your pelvis where the bottom of the spine (the sacrum) meets the wing-like hip bones (the ilium) on each side. They are built to move barely at all, held together by thick ligaments, but they do transfer load from your spine into your legs every step you take. SI joint dysfunction is pain coming from one of those joints. It accounts for roughly 15-25% of chronic low back pain. It can flare up from a sudden twisting injury, pregnancy (the hormones that loosen the pelvis for childbirth), a difference in leg length, extra strain after a previous lumbar spinal fusion, or an inflammatory arthritis condition like ankylosing spondylitis.

The classic pattern is pain in the lower back, buttock, and sometimes the back of the thigh, almost always on just one side. Pressing on the dimple at the back of the pelvis usually reproduces it.

Symptoms

what you may notice

Pain in the lower back and buttock, usually on one side, centered right over the dimple at the back of the pelvis
Pain that may travel down the back of the thigh (but rarely below the knee, which helps distinguish it from sciatica)
Aching that worsens with prolonged standing, stair climbing, or getting in and out of a car
Pain that flares when you shift weight onto one leg or roll over in bed
Stiffness in the lower back and hips first thing in the morning
A catching or clicking sensation at the back of the pelvis with certain movements

Diagnosis

exam first, imaging second

No single exam test nails the diagnosis. Your provider runs through a cluster of maneuvers (moving your hip into specific positions, applying pressure to the joint) and counts how many reproduce your pain. The most reliable confirmation is an image-guided injection of numbing medicine directly into the SI joint: if your pain disappears for the few hours the medicine works, that is strong proof the SI joint is the source. This injection is an interventional procedure that OSI does not perform; when it is the right next step to pinpoint the source, OSI refers you to a pain management specialist who provides it, and your diagnostic workup and non-operative care continue with us. An MRI is added when an inflammatory arthritis is suspected.

Treatment Path

how care progresses

Most SI joint pain settles with non-operative care, and the goal is to make the joint move less while the muscles around it do more of the work. The steps below are the order we usually introduce them, each one added on top of the last rather than instead of it.

Physical therapy

Targeted PT focuses on stabilizing the pelvis: strengthening the deep core, glutes, and the muscles that control how your pelvis tilts when you walk, so the muscles take over the work of steadying the joint.

SI joint belt / orthotic

A wide elastic belt worn around the pelvis (an SI joint belt) gently squeezes the joint together. For SI pain driven by an overly mobile joint, this often takes the edge off enough to make rehab more productive.

NSAIDs

An over-the-counter anti-inflammatory like ibuprofen or naproxen calms the joint inflammation enough to make the PT and bracing work easier to tolerate.

If Surgery Is Truly Needed

rare for most patients

Surgery helps only a small minority of spine patients, usually those with a specific structural problem plus a nerve issue that is not getting better with a structured non-operative trial. When that step is genuinely warranted, it falls outside the care OSI provides, so we refer you to a spine surgeon. OSI does not perform or coordinate spine surgery; your non-operative care stays with us.

Frequently Asked

questions we hear in clinic

Where does SI joint pain show up?

The classic pattern is pain in the lower back and buttock, almost always on just one side, centered right over the dimple at the back of the pelvis. It can travel down the back of the thigh, but it rarely goes below the knee, which helps tell it apart from sciatica.

How is it different from sciatica?

SI joint pain tends to stay in the lower back, buttock, and back of the thigh, and rarely radiates below the knee. That pattern is one of the things that helps distinguish it from sciatica.

What brings it on?

It can flare from a sudden twisting injury, pregnancy (the hormones that loosen the pelvis for childbirth), a difference in leg length, extra strain after a previous lumbar spinal fusion, or an inflammatory arthritis condition such as ankylosing spondylitis.

How do you confirm the SI joint is the source?

No single exam test nails the diagnosis, so your provider runs through a cluster of maneuvers and counts how many reproduce your pain. The most reliable confirmation is an image-guided injection of numbing medicine directly into the SI joint: if your pain disappears for the few hours the medicine works, that is strong proof the joint is the source. This injection is an interventional procedure that OSI does not perform; when it is the right next step, OSI refers you to a pain management specialist who provides it, and your care continues with us.

Will I need an MRI?

Not in most cases. An MRI is added when an inflammatory arthritis is suspected.

Does an SI joint belt help?

For SI pain driven by an overly mobile joint, a wide elastic belt worn around the pelvis gently squeezes the joint together, which often takes the edge off enough to make rehab more productive.

Will I need surgery?