Sacroiliac joint dysfunction affects 15 to 30 percent of people with chronic low back pain, yet many patients never receive a clear explanation of what caused their condition. Doctors identify seven primary causes: trauma and injury, arthritis, joint hypermobility or hypomobility, pregnancy-related changes, gait abnormalities, prior spine surgery, and inflammatory conditions. For instance, a 55-year-old who experienced a fall on the stairs might develop sacroiliac joint dysfunction from torn ligaments, while a 38-year-old woman two years postpartum continues to have pain from ligament laxity that never fully resolved.
Understanding which cause is driving your pain matters because the treatment approach differs significantly depending on whether the joint is moving too much, too little, or has sustained structural damage. This article walks through each of the seven causes that physicians encounter in clinical practice, explains the underlying mechanism, and highlights what distinguishes each cause from the others. You’ll learn why some causes are more common in women, how prior surgery increases risk, and what symptoms might point to each specific cause.
Table of Contents
- How Trauma and Injury Trigger Sacroiliac Joint Dysfunction
- Arthritis and Inflammatory Diseases Affecting the Sacroiliac Joint
- Hypermobility and Hypomobility—The Paradox of Movement
- Pregnancy and the Postpartum Period—Hormonal and Biomechanical Changes
- Gait Abnormalities and Biomechanical Misalignment
- Prior Spine Surgery and Failed Back Surgery Syndrome
- Understanding Risk Factors and the Broader Clinical Picture
- Conclusion
How Trauma and Injury Trigger Sacroiliac Joint Dysfunction
Direct falls, motor vehicle accidents, and sports injuries are among the most straightforward causes of sacroiliac joint dysfunction. When you fall hard onto your buttocks or experience a sudden impact to the lower back or pelvis, the ligaments that stabilize the sacroiliac joint can stretch, tear, or partially rupture. These ligaments are critical shock absorbers—they hold the sacrum (the base of your spine) and the ilium (hip bone) in proper alignment, allowing only a few millimeters of movement. Once torn, they lose their ability to support the joint effectively.
A typical example is a skier who catches an edge and falls backward onto the slope, or a construction worker who drops from scaffolding and lands on their side. The initial pain may feel like severe bruising, but as swelling decreases over weeks, patients often report persistent deep pain in the lower back or buttocks. The challenge with trauma-related cases is that standard imaging (X-rays) may show no obvious fracture, leading some doctors to miss the diagnosis initially. However, ligament tears do appear on MRI imaging, which is why advanced imaging becomes important when history suggests a fall or accident.
Arthritis and Inflammatory Diseases Affecting the Sacroiliac Joint
While many people associate arthritis with knees or hands, the sacroiliac joint is equally vulnerable to inflammatory and degenerative joint disease. Osteoarthritis—the “wear and tear” form—develops when cartilage in the joint deteriorates over time, leading to bone-on-bone contact, osteophyte formation (bone spurs), and joint-space narrowing visible on imaging. Ankylosing spondylitis is a more aggressive inflammatory disease that progressively erodes the sacroiliac joint itself, often causing severe fusion and loss of mobility. Additionally, rheumatoid arthritis, psoriatic arthritis, and even gout can trigger sacroiliitis (inflammation of the joint).
The prevalence of arthritis-related sacroiliac joint dysfunction increases with age, particularly in people over 50. A key distinction: osteoarthritis typically develops in one joint or asymmetrically (affecting one side more than the other), whereas ankylosing spondylitis often affects both joints symmetrically and is associated with systemic symptoms like morning stiffness and fatigue. If you have a known inflammatory condition like Crohn’s disease or ulcerative colitis, be aware that intestinal inflammation can spill over and cause inflammation in the sacroiliac joint as well. This is important because treating the underlying inflammatory disease may be necessary to resolve the joint pain.
Hypermobility and Hypomobility—The Paradox of Movement
Not all sacroiliac joint dysfunction stems from injury or disease. Some patients suffer from hypermobility—excessive movement in the joint beyond what is normal. This instability causes pain deep in the lower back, hip, or even radiating into the groin. The ligaments and muscles around the joint cannot maintain proper stability, so the sacrum moves too freely during walking, sitting, or standing. Other patients have the opposite problem: hypomobility or fixation, where the joint becomes locked or restricted in its movement.
This causes unilateral (one-sided) lower back or buttocks pain that may radiate down the leg, mimicking sciatica. These two conditions present a treatment paradox. Someone with hypermobility needs stabilization exercises, bracing, or techniques to reduce joint movement, whereas someone with hypomobility needs mobilization techniques to restore normal joint play. A physical therapist performs specific tests—such as assessing how the sacroiliac joint moves during certain movements—to determine whether the joint is too mobile or too fixed. Treating hypermobility with aggressive mobilization, or treating hypomobility with stabilization alone, can actually worsen pain. This is why accurate diagnosis of which problem exists is essential before starting physical therapy.
Pregnancy and the Postpartum Period—Hormonal and Biomechanical Changes
Pregnancy is one of the most common causes of sacroiliac joint dysfunction in women. During pregnancy, the body releases relaxin and other hormones that loosen ligaments throughout the body to allow the pelvis to widen for childbirth. At the same time, extra body weight shifts the center of gravity forward, increasing load on the sacroiliac joints. The combination of ligament laxity and increased weight causes increased cartilage wear and an inflammatory response in the joint.
Many women expect sacroiliac pain to resolve after delivery, but ligament healing takes months and sometimes longer. Some women experience improvement within weeks postpartum, while others have pain that persists for years. This variation may depend on whether the joint sustains additional trauma during delivery, the level of physical activity during recovery, and whether pelvic floor and deep stabilizer muscles are retrained. Bracing during pregnancy, proper body mechanics during labor, and targeted postpartum rehabilitation can reduce the risk of long-term dysfunction.
Gait Abnormalities and Biomechanical Misalignment
How you walk directly impacts how much stress your sacroiliac joint experiences. Scoliosis (spinal curvature), true leg-length discrepancies (one leg is actually shorter due to bone development), and apparent leg-length differences (caused by muscle tightness or pelvic misalignment) all alter the alignment of the pelvis and sacroiliac joint. Additionally, an Achilles tendon rupture, ACL injury, or other lower-limb injury changes your gait pattern as you compensate for the injured side. Over time, this uneven loading wears the sacroiliac joint on one side more than the other.
A patient with mild scoliosis might not notice pain until middle age when cumulative stress finally becomes intolerable. Similarly, someone who suffered a knee injury years ago may have unconsciously altered their gait to favor the other leg, and the resulting sacroiliac joint pain develops years after the original injury. A physical therapist or sports medicine physician can assess your gait with video analysis or during a functional movement screen to identify these patterns. Addressing the underlying cause—whether that’s correcting a leg-length difference with an orthotic insert, strengthening a weak knee, or working with posture—can reduce sacroiliac joint stress.
Prior Spine Surgery and Failed Back Surgery Syndrome
Lumbar fusion surgery, particularly when the fusion extends down to the sacrum, significantly increases stress on the sacroiliac joints. By rigidly connecting vertebrae above, fusion surgery causes the sacroiliac joint to absorb more rotational and bending stress. Research shows that 40 to 63 percent of patients with Failed Back Surgery Syndrome—chronic pain and disability after lumbar spine surgery—have the sacroiliac joint as the primary pain source, not the original surgical site.
If you have had lumbar fusion surgery and continue to have low back pain below the level of the fusion, sacroiliac joint dysfunction should be investigated. The challenge is that some surgeons and patients assume continued pain must mean the fusion did not work or that more surgery is needed, when actually the adjacent joint is the culprit. Sacroiliac joint bracing, targeted physical therapy, and in some cases diagnostic injections and radiofrequency ablation can address this pain without reoperation.
Understanding Risk Factors and the Broader Clinical Picture
Beyond the seven primary causes, several risk factors increase vulnerability to sacroiliac joint dysfunction: obesity puts extra load on the joints, prolonged sitting with weak pelvic muscles reduces stabilization, contact sports and heavy lifting with poor technique cause repetitive stress, and older age increases the likelihood of degenerative changes. Women are more frequently affected than men, with a bimodal age distribution—one peak in younger women after pregnancy or sports injury, and another peak in older women from arthritis and degeneration. Recognizing these risk factors matters because they inform prevention strategies.
A 30-year-old athlete can reduce future risk through proper training technique and core strengthening. A 60-year-old with early osteoarthritis can slow progression with activity modification and anti-inflammatory measures. And a woman planning pregnancy can benefit from pelvic floor physical therapy before conception to build stronger stabilizing muscles.
Conclusion
Sacroiliac joint dysfunction has multiple distinct causes, and identifying the correct cause is the foundation of effective treatment. Whether your pain stems from a fall, arthritis, pregnancy-related changes, movement problems, gait abnormalities, or prior surgery, the underlying mechanism determines which treatments will help and which might make things worse. Many of these causes are diagnosed through a combination of clinical examination, movement assessment, and imaging—no single test confirms sacroiliac joint dysfunction on its own.
If you experience persistent lower back pain, buttocks pain, or pain that radiates into the groin or down one leg, discuss sacroiliac joint dysfunction with your physician. A clear diagnosis of the cause opens the door to targeted treatment: stabilization or mobilization exercises, bracing, addressing gait problems, managing inflammation, or in some cases, image-guided injections. Early recognition prevents years of misdirected treatment and unnecessary tests.
