OVERVIEW

What is Condensing Osteitis?

Condensing osteitis is a non-infectious inflammatory condition characterized by bone sclerosis, which can affect multiple joints such as the clavicle, sternoclavicular joint, mandible, and ilium. The most common site is the ilium. Additionally, periapical condensing osteitis may occur around the roots of teeth in the maxilla or mandible, representing a chronic periapical inflammation.

What is Iliac Condensing Osteitis?

Iliac condensing osteitis, also known as osteitis condensans ilii (OCI), is a non-infectious inflammation characterized by bone sclerosis around the sacroiliac joint, particularly in the lower two-thirds of the ilium. The joint space usually remains unchanged.

Most patients have no clinical symptoms and the condition develops insidiously, often discovered incidentally on X-rays. A small number of patients may experience lumbosacral pain.

Iliac condensing osteitis is a benign condition and does not lead to serious consequences. Asymptomatic cases require no treatment, while symptomatic cases can be managed with symptomatic relief.

Who is Most Commonly Affected by Iliac Condensing Osteitis?

Over 90% of patients are women aged 20–40, with a higher prevalence during late pregnancy and postpartum. Reports indicate a detection rate of up to 18.82% among women with low back or leg pain. Male cases are rare.

Is Iliac Condensing Osteitis the Same as Ankylosing Spondylitis?

They are two distinct conditions, with iliac condensing osteitis being much milder than ankylosing spondylitis.

Clinically, iliac condensing osteitis is often misdiagnosed as ankylosing spondylitis because the latter also commonly presents with lower back and/or hip pain, and imaging (X-ray or CT) may show bone sclerosis in the sacroiliac joint. Therefore, additional diagnostic tests are necessary for accurate differentiation.

In very rare cases, both conditions may coexist, requiring individualized diagnosis and treatment.

SYMPTOMS

What are the clinical manifestations of iliac osteitis condensans?

• Asymptomatic: Most patients do not exhibit obvious clinical symptoms and are often incidentally discovered during X-ray imaging.
• Pain: A small number of patients may experience chronic, intermittent dull or aching pain in the lower back or sacral (buttock) region, without sharp or severe pain. The discomfort may radiate to one or both buttocks and the posterior thigh but does not follow the path of the sciatic nerve. Symptoms often worsen with walking, standing, weight-bearing, or fatigue and improve with adequate rest.

During physical examination, doctors may observe an increased lumbosacral angle, tenderness and muscle tension upon palpation of the lumbosacral region, as well as positive results in pelvic separation and compression tests and the "4" test.

CAUSES

What are the causes of iliac osteitis condensans?

The exact cause remains unknown, but it is generally believed that mechanical damage affects the auricular surface of the ilium and triggers early arthritis.
Over 90% of patients with this condition are married women who have given birth, with higher prevalence during late pregnancy or postpartum. It can also occur after chronic infections of the urinary tract or female adnexa, or other pelvic infections. Trauma to the buttocks or sacral region may also induce or cause this condition.

Evidently, pregnancy, childbirth, trauma, and pelvic infections are the primary factors contributing to the onset of this disease. A possible explanation is that during late pregnancy or postpartum, hormonal changes lead to relaxation of the sacroiliac ligaments, resulting in joint instability. Abnormal mechanical stress or chronic injury may then cause tears in the sacroiliac ligaments and local bone ischemia or hypoxia, impairing blood supply to the area. This triggers hyperplastic and degenerative reactions, eventually leading to bone sclerosis as collagen fibers become denser.

DIAGNOSIS

How to diagnose osteitis condensans ilii?

• Initial diagnosis can be made through X-ray imaging.
• For patients with unclear symptoms requiring differential diagnosis, CT or magnetic resonance imaging (MRI) is necessary.
• If differentiation remains difficult (e.g., distinguishing from ankylosing spondylitis), laboratory tests such as HLA-B27, immunoglobulins, and erythrocyte sedimentation rate (ESR) may be performed.

What are the imaging features of osteitis condensans ilii on X-ray or CT?

The sacroiliac joint space appears regular and clear. The iliac auricular surface near the sacroiliac joint shows increased bone density, presenting as a uniformly dense, sharply demarcated sclerotic band with disappearance of trabeculae and absence of bone destruction.

How to differentiate osteitis condensans ilii from ankylosing spondylitis?

Ankylosing spondylitis also commonly manifests as low back pain and/or buttock pain, with sacroiliac joint sclerosis visible on X-ray or CT, making it easily confused with osteitis condensans ilii. However, they differ in the following aspects:

• Pain characteristics differ: Ankylosing spondylitis-related low back pain often involves morning stiffness that improves with activity but worsens with rest. Patients may experience severe nocturnal pain disrupting sleep and difficulty turning over. In contrast, osteitis condensans ilii pain typically improves with rest and worsens with physical labor or prolonged walking - the opposite clinical pattern.
• Different imaging features: Ankylosing spondylitis causes early sacroiliac joint destruction with simultaneous bone erosion and sclerosis, progressing to bony ankylosis and spinal involvement, often with joint space narrowing. Osteitis condensans ilii shows intact or normal sacroiliac joint surfaces without destructive changes, maintaining normal joint space.
• Different affected populations: Ankylosing spondylitis predominantly affects young males, while osteitis condensans ilii mainly occurs in married, childbearing-aged women.
• Different laboratory findings: Over 90% of ankylosing spondylitis patients test positive for HLA-B27, often with elevated ESR. Blood tests for osteitis condensans ilii patients typically show no abnormalities.

TREATMENT

Which department should I visit for iliac osteitis condensans?

Orthopedics.

Does iliac osteitis condensans require hospitalization?

No.

How is iliac osteitis condensans treated?

This condition is self-limiting with a good prognosis and generally leaves no sequelae, so treatment is mainly symptomatic. Over-treatment should be avoided.

• Asymptomatic individuals do not require treatment.
• Patients with mild symptoms can alleviate pain through methods such as proper bed rest, using an elastic waistband for protection during activity, hot compresses, physical therapy, or acupuncture.
• Patients with moderate to severe symptoms (i.e., those affecting walking or work) can take nonsteroidal anti-inflammatory drugs (NSAIDs) or receive local injection therapy, along with joint protection using a brace. After pain relief, abdominal muscle exercises should be actively performed, and an elastic waistband should continue to be used for protection.
• For patients with extremely severe or stubborn symptoms who do not respond to conservative treatment, sacroiliac joint fusion surgery may be performed. Generally, only the upper joint fusion is needed, avoiding full joint fusion to prevent accidental injury to the superior gluteal artery, which could lead to serious consequences.

Can iliac osteitis condensans cause complications or sequelae?

Generally not.

DIET & LIFESTYLE

What should patients with iliac osteitis condensans pay attention to in their diet?

Diet has no impact on this condition, so patients do not need to avoid any specific foods. Maintaining a healthy, regular, and balanced diet is sufficient.

What should patients with iliac osteitis condensans pay attention to in daily life?

• Avoid excessive worry or anxiety, and cultivate a positive mindset;
• Ensure adequate rest and avoid overexertion;
• Engage in regular exercise, especially abdominal muscle training, when physical condition permits.

PREVENTION

Can iliac osteitis condensans be prevented?

Since the exact cause of iliac osteitis condensans remains unclear, there are no particularly effective preventive measures.

As the condition is commonly seen in women after pregnancy, childbirth, trauma, or pelvic infections, such individuals should focus on maintaining good lifestyle habits, ensuring perineal hygiene, engaging in physical exercise, boosting immunity, and reducing the risk of traumatic infections. These measures may help lower the likelihood of developing iliac osteitis condensans.