What is SI joint dysfunction?
The sacroiliac joints connect the base of the spine to the pelvis on each side. They move very little, but they transmit the entire load of the upper body into the legs. When a joint becomes irritated (through wear, injury, pregnancy, altered gait, or the extra stress that follows a lumbar fusion), it can become a genuine source of pain.
Symptoms
- Pain low and off to one side, just below the belt line
- Pain when rolling over in bed, standing from a chair, or climbing stairs
- Pain into the groin or the back of the thigh, usually stopping above the knee
- Tenderness over one dimple of the low back rather than the midline
- Difficulty sitting for long periods, or a preference for shifting weight to one side
Urgent
Come in promptly if you cannot bear weight after a fall, or if you develop numbness in the saddle area or any change in bowel or bladder control.
How it is diagnosed
This is a diagnosis made largely by examination rather than by scan. A series of maneuvers load the joint in different ways; reproducing the pain across several of them points strongly to the SI joint. Imaging is used mainly to exclude other causes, since the joint often looks unremarkable. A diagnostic injection that relieves the pain is the most direct confirmation. Physical exam maneuvers include:
- Distraction test — posteriorly directed pressure on both ASISs stresses the anterior SI joints.
- Thigh thrust test — with the hip flexed, axial force through the femur produces posterior shear across the SI joint.
- Compression test — with the patient side-lying, downward pressure over the iliac crest compresses the SI joints.
- Sacral thrust test — anterior force applied over the sacrum with the patient prone stresses the SI joints.
- Gaenslen test — one hip is maximally flexed while the opposite hip is extended, creating torsional stress across the SI joints.
- FABER (Patrick) test — flexion, abduction, and external rotation of the hip can reproduce posterior SI-region pain.
Non-surgical treatment
Physical therapy aimed at the pelvis, hips, and core is the mainstay, alongside activity modification and anti-inflammatory medication where appropriate. A supportive belt helps some people. Therapeutic injection can provide relief and make rehabilitation more productive. The large majority of cases are managed this way.
When surgery is considered
SI joint fusion is considered only after that sequence has been worked through and the joint has been confirmed as the pain source, typically by a clear response to injection. It is a targeted procedure for a specific, well-identified problem rather than a general treatment for low back pain.