Sacroiliac Joint Degenerative Changes: Causes & Symptoms

Degenerative changes in the sacroiliac joint are remarkably common, showing up on imaging in roughly two-thirds of adults who have no pain at all. A study of asymptomatic people found a prevalence of about 65%, climbing to over 90% in those in their eighties.¹ That high rate in people without symptoms is a crucial detail, because it means that seeing degeneration on a scan does not automatically explain someone’s pain. The causes range from simple aging to pregnancy-related changes, prior surgery, and structural imbalances, while the symptoms can mimic low back problems closely enough to send both patients and clinicians on a long diagnostic detour.

What the Sacroiliac Joint Actually Does

The sacroiliac joint sits where the base of the spine (the sacrum) meets the broad wing-shaped bones of the pelvis (the ilia). Its main job is transferring the weight of your upper body into your legs. Unlike a hip or knee, it barely moves: flexion and extension account for only about three degrees, with even less rotation and side-bending.² That near-immobility is by design. The sacrum is wedged tightly between the two hip bones, and a dense network of ligaments and muscles locks everything in place, creating what researchers call a “self-bracing” effect that protects the joint from shearing apart under load.³

Because the joint’s surfaces are relatively flat rather than ball-and-socket shaped, it relies heavily on that surrounding architecture for stability. When the ligaments, muscles, or bony surfaces degrade over time, the joint becomes more susceptible to abnormal loading, and degeneration follows. The cartilage lining the joint wears down, bony spurs form at the margins, and the subchondral bone underneath the cartilage thickens (a process called sclerosis). Those three changes, osteophytes, sclerosis, and joint space narrowing, are the hallmarks of sacroiliac joint degeneration on any imaging study.

How Common These Changes Are, and Who Gets Them

A large CT-based study of over 800 people in the general population found that sclerosis appeared in about 46% and osteophytes in about 47%, with both increasing in a nearly straight-line fashion with age. Osteophytes peaked at close to 78% in people aged 75 and older. Joint space narrowing was rarer overall, around 9%, but still climbed to roughly 27% in the oldest age group.⁴ The takeaway is that some degree of wear-and-tear change in this joint is essentially a normal part of aging. The separate study of asymptomatic adults that found 65% prevalence also noted that about 30% had what the researchers categorized as substantial degeneration, yet none of them had sacroiliac pain.¹

Sex differences matter here in unexpected ways. Women were far more likely to develop bony spurs along the back (dorsal) edge of the joint, with more than four times the odds compared to men. Men, on the other hand, were more likely to develop spurs along the front (ventral) edge.⁴ This pattern likely reflects differences in pelvic anatomy and loading patterns. Women have a wider pubic angle and less curvature in the sacroiliac joint surfaces, which alters how forces distribute across the joint during standing, walking, and especially pregnancy.

The Major Causes and Risk Factors

Age is the single biggest driver. The relationship between getting older and developing degenerative changes here is about as linear as biology gets. But aging alone does not explain why some people develop pain while others coast along with worn joints and no complaints. Several other factors speed up degeneration or push it past the threshold where symptoms appear.

Pregnancy and Postpartum Changes

During pregnancy, the body produces hormones like relaxin and estrogen that loosen the ligaments holding the pelvis together. Combined with weight gain, a shifting center of gravity, and increased pressure on the pelvic floor, these changes put the sacroiliac joints under unusual stress. Women already have greater sacroiliac joint mobility than men because of their pelvic geometry, and pregnancy amplifies that difference significantly.⁵ For many women, the ligaments tighten back up after delivery and symptoms resolve. But repeated pregnancies or cases where the ligaments remain lax can set the stage for accelerated wear on the joint surfaces.

Prior Spinal Fusion Surgery

When segments of the lumbar spine are surgically fused, the joints above and below the fusion have to absorb forces that the fused segments used to handle. The sacroiliac joint sits directly below the most common fusion sites, making it a frequent victim of this redistribution. A study of over half a million patients who had posterior spinal fusions found that about 1.1% eventually needed a separate sacroiliac joint fusion. The risk was higher in women, people with obesity, those with fibromyalgia or diabetes, smokers, and especially in patients whose fusions spanned longer segments of the spine. Fusing seven or more vertebral levels roughly doubled the odds.⁶ While 1.1% sounds small, it represents thousands of patients, and many more likely develop sacroiliac symptoms without progressing to surgery.

Leg Length Discrepancy

When one leg is even moderately longer than the other, the pelvis tilts, and the sacroiliac joints on each side absorb unequal loads. A biomechanical modeling study showed that peak stresses on the sacroiliac joint surfaces increased progressively with each centimeter of leg length difference, and that correcting the discrepancy with shoe lifts or surgical adjustment should reduce that extra loading.⁷ The real-world implication is that people with a noticeable difference in leg length who develop one-sided sacroiliac pain may benefit from something as simple as a heel lift.

Anatomical Variants

Not everyone’s sacroiliac joint looks the same. Some people have extra bony formations, called an iliosacral complex, or other structural variations in the joint’s shape. Research on young, asymptomatic adults found that those with anatomical variations already showed significantly more sacroiliac joint degeneration than those with typical anatomy.⁸ You cannot change your joint anatomy, but knowing about these variants can help explain why some younger adults develop degeneration earlier than expected.

What Sacroiliac Degeneration Feels Like

The symptom picture is frustratingly nonspecific, which is a big part of why sacroiliac problems often go unrecognized or get blamed on the lumbar spine. In a study of 50 patients with confirmed sacroiliac joint pain (verified by diagnostic injections), 94% reported buttock pain and 72% had pain in the lower back. Half described pain radiating into the leg, and about 28% had pain below the knee. A smaller group, about 14%, reported groin pain.⁹

That overlap with lumbar disc problems is striking. Buttock pain plus leg pain below the knee sounds a lot like sciatica, and lower-back pain is, of course, the most generic orthopedic complaint imaginable. The study found 18 different patterns of pain referral, meaning the joint can send pain signals to a wide variety of locations. Age played a role too: younger patients were more likely to feel pain traveling all the way down to the foot, while older patients tended to keep their pain closer to the buttock and low back.⁹

Beyond pain location, people with sacroiliac degeneration often notice that symptoms flare with prolonged sitting, standing from a seated position, climbing stairs, or rolling over in bed. The pain tends to be one-sided, centered just below and to the side of the lower back. Stiffness after long periods of inactivity is common, improving with gentle movement but worsening with sustained loading. None of these features are exclusive to sacroiliac problems, which is precisely why diagnosis requires more than a symptom checklist.

Why It Gets Mistaken for Other Conditions

The imaging overlap is just as tricky as the symptom overlap. On plain X-rays, sacroiliac degeneration produces narrowing of the joint space, sclerosis along the bone surfaces, and osteophytes, which can look remarkably similar to ankylosing spondylitis, an inflammatory form of arthritis that typically strikes younger adults. The distinction matters enormously because the two conditions require completely different treatments. Research has shown that the bony bridging in degenerative disease tends to form in front of and outside the actual joint cavity (paraarticular osteophytes), while ankylosing spondylitis causes fusion within the joint itself. The sclerosis pattern also differs: degeneration favors the top and bottom margins of the joint, whereas inflammatory sacroiliitis tends to produce more diffuse, bilateral changes.¹⁰

MRI has become the standard for evaluating suspected inflammatory sacroiliitis, particularly in younger patients being screened for spondyloarthritis. But MRI findings that look like inflammation can show up in degenerative disease, pregnancy-related changes, osteitis condensans ilii (a benign sclerotic condition common in women), and even stress fractures. Overreading these MRI findings as early inflammatory arthritis leads to misdiagnosis and sometimes unnecessary treatment with potent immunosuppressive medications.¹¹ The clinical context, the patient’s age, symptom pattern, and blood work, has to guide interpretation of any imaging.

How Sacroiliac Joint Pain Gets Diagnosed

There is no single physical exam test that nails the diagnosis. Clinicians typically use clusters of provocation tests, maneuvers that stress the sacroiliac joint in specific ways to see whether they reproduce the patient’s pain. A meta-analysis of studies evaluating these test clusters found they are helpful but far from definitive. When the tests are positive, the probability that the pain is actually coming from the sacroiliac joint rises from around 20% (the estimated background rate) to about 35%. When the tests are negative, the probability drops to around 8%.¹² Useful for screening, but not enough to commit to a diagnosis on their own.

Newer provocation test combinations may improve accuracy. One set of composite tests showed substantially better performance than traditional methods at identifying chronic sacroiliac joint dysfunction, particularly when trying to distinguish it from lumbar disc herniation, which is one of the most common mimics.¹³ Still, the confirmation step in most cases is a diagnostic injection. A small amount of local anesthetic is injected directly into the sacroiliac joint under imaging guidance. If the patient’s pain drops substantially, the joint is considered the source. Fluoroscopy-guided injections are the gold standard because of their high accuracy in placing the needle within the joint space, with one series showing 76% mean pain relief compared to 56% for landmark-based approaches.¹⁴ Ultrasound-guided injections offer a radiation-free alternative with decent but lower accuracy.¹⁵

Managing Degenerative Sacroiliac Pain

Because degeneration on imaging is so common in pain-free people, treatment focuses on symptoms and function rather than trying to reverse the structural changes. The first line is almost always conservative: physical therapy, activity modification, and anti-inflammatory medications. Strengthening the muscles that stabilize the pelvis, particularly the deep core muscles, the erector spinae along the lower spine, and the hamstrings, can improve how forces distribute across the joint and reduce pain. Even small-scale evidence supports this approach: targeted strengthening exercises for the sacroiliac stabilizers have been shown to eliminate pain provocation test findings and significantly reduce pain scores in as little as three weeks.¹⁶

When conservative measures are not enough, therapeutic injections of corticosteroid into the joint can provide temporary relief. Radiofrequency ablation, which uses heat to disable the small nerves that carry pain signals from the joint, is another option with a growing evidence base. Platelet-rich plasma injections have also been explored, though the evidence remains limited to a handful of clinical trials and case reports.¹⁷

For patients who fail all other options, minimally invasive sacroiliac joint fusion has become an increasingly common surgical procedure. The operation involves placing small titanium implants across the joint to promote bony fusion and eliminate painful motion. Five-year follow-up data from one series showed bony bridging across the joint in 87% of patients, with no evidence of implant loosening or migration.¹⁸ The procedure is not for everyone, and the key to a good outcome is making sure the sacroiliac joint was genuinely the pain source before operating, which circles back to the importance of a thorough diagnostic workup.

The Sedentary Factor

Modern lifestyles contribute to sacroiliac trouble in ways that get less attention than they deserve. Prolonged sitting reduces blood flow to the muscles and ligaments supporting the pelvis, weakens the gluteal muscles that are critical for sacroiliac stability, and places the joint in a loaded, flexed position for hours at a time. Desk workers frequently develop sacroiliac symptoms not because their joints are structurally worse than anyone else’s, but because the muscles that should be absorbing and distributing pelvic forces have essentially gone offline. The stabilization exercise study mentioned earlier specifically recruited a sedentary worker and demonstrated meaningful improvement with a targeted strengthening program.¹⁶ For people with desk jobs, regular movement breaks and a few targeted exercises may do more to prevent sacroiliac pain than any medication or injection.

The broader point is that sacroiliac degeneration is a near-universal feature of aging joints, but pain from it is not. The gap between structural changes and symptoms leaves room for prevention and management strategies that focus on how the joint is loaded rather than what the joint looks like. Keeping the surrounding muscles strong, addressing leg-length discrepancies, managing body weight, and avoiding prolonged static postures are all modifiable factors that influence whether a worn joint stays quiet or starts complaining.

When Degeneration Is Actually Something Else

Because so many conditions can affect the sacroiliac joint and produce overlapping findings on imaging, it is worth knowing about a few common mimics beyond ankylosing spondylitis. Osteitis condensans ilii causes dense sclerosis on the iliac side of the joint, typically in women of childbearing age, and is usually asymptomatic or mildly symptomatic. It can look alarming on a CT or X-ray but does not progress to joint destruction. Infectious sacroiliitis, while rare, produces a very different clinical picture: acute onset, fever, and severely restricted movement, often in someone with an identifiable risk factor like recent surgery or intravenous drug use. Sacral stress fractures, particularly insufficiency fractures in older adults with osteoporosis, cause sacroiliac-region pain that can be mistaken for joint disease until MRI reveals the fracture line running through the sacrum itself rather than through the joint.¹¹

SAPHO syndrome (a rare inflammatory condition involving skin, bone, and joints) and hyperparathyroidism can also produce sacroiliac changes that look like degeneration or inflammation on imaging. These are uncommon enough that most clinicians would not consider them first, but they are worth investigating when the clinical picture does not quite fit the expected pattern for garden-variety osteoarthritis or spondyloarthritis. The recurring theme in sacroiliac joint evaluation is that no single test, image, or symptom tells the whole story. Accurate diagnosis depends on layering clinical findings, imaging, and sometimes diagnostic injections to build a case that points convincingly toward the joint as the source of the problem.