Lower back pain is a frequent complaint. While many people suspect issues with the lumbar spine or hip, chronic lower back discomfort often originates from the sacroiliac (SI) joint. The SI joint is a robust, paired connection point linking the triangular sacrum (at the base of the spine) to the ilium (the large, uppermost part of the pelvis). This joint transfers the weight of the upper body to the lower limbs. Bilateral sacroiliac degenerative joint disease is a specific type of arthritis impacting both of these joints.
Anatomy and Definition of Sacroiliac Degenerative Joint Disease
The sacroiliac joint functions primarily as a weight-bearing structure that absorbs shock between the torso and the legs. Although classified as a synovial joint, its movement is extremely limited, typically allowing only a few millimeters of motion. This minimal motion is tightly controlled by an intricate and strong network of ligaments, including the interosseous sacroiliac ligament, which is considered one of the strongest in the body. The stability provided by these dense ligaments is necessary to transfer substantial force from the spine to the lower extremities.
Degenerative joint disease, also known as osteoarthritis, occurs when the protective cartilage covering the ends of the bones gradually wears away. In the SI joint, this erosion causes the underlying bones to rub against one another. This friction leads to inflammation, bony changes, and the formation of bone spurs, resulting in pain and reduced function. The term “bilateral” indicates that this degenerative process is present in both the left and right sacroiliac joints simultaneously.
Common Causes and Contributing Factors
The primary cause of sacroiliac degenerative joint disease is advancing age, as decades of use lead to the gradual wear and tear of the articular cartilage. Trauma, such as a fall or motor vehicle accident, can accelerate degeneration by damaging the joint surfaces or surrounding ligaments.
Biomechanical imbalances and altered gait patterns also contribute by unevenly loading the SI joints. Conditions like scoliosis, a persistent limp, or a leg length discrepancy force one joint to bear a disproportionate amount of weight. Previous spinal surgery, particularly lumbar fusion, increases stress on the SI joint because limiting motion in the lumbar spine shifts mechanical demands to the adjacent joints. Additionally, hormonal changes and altered posture during pregnancy place temporary stress on the pelvic girdle.
Confirming the Diagnosis
Diagnosing bilateral SI degenerative joint disease is complex because the pain often mimics symptoms of other lower back or hip issues. The initial step involves a thorough physical examination where a physician performs specific movement tests designed to provoke pain originating from the SI joint. A diagnosis is strongly suggested when a patient reports pain during three or more of these provocation tests, which include:
- Thigh Thrust
- Distraction
- Compression
- FABER (Flexion, Abduction, External Rotation) test
Imaging studies are used to rule out other causes of pain and visualize structural changes. X-rays can show joint space narrowing or osteophytes, characteristic of degenerative arthritis. Computed tomography (CT) scans offer more detailed images of the bone structure to assess the extent of degeneration. However, imaging alone is insufficient to confirm the SI joint as the definitive pain source, as degenerative changes can exist without causing symptoms. The diagnostic gold standard is an image-guided injection of a local anesthetic directly into the SI joint. If the patient experiences significant pain relief, typically 50% to 75% or more, immediately after the injection, the SI joint is confirmed as the pain generator.
Managing and Treating the Condition
Management of bilateral SI degenerative joint disease begins with conservative, non-surgical approaches. First-line treatments include nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce pain and inflammation. Physical therapy is a fundamental component, focusing on exercises to strengthen pelvic stabilizing muscles and improve biomechanics. A sacroiliac belt may also be recommended to provide external support and limit excessive joint motion.
When conservative measures fail, interventional procedures are considered. Image-guided corticosteroid injections deliver anti-inflammatory medication directly into the joint space for temporary pain relief. For longer-lasting relief, radiofrequency ablation (RFA) can be performed. RFA uses thermal energy to create a lesion on the small nerves supplying the joint, interrupting pain signal transmission. This minimally invasive technique is used for patients who experience temporary relief from diagnostic blocks.
Surgical intervention is reserved for severe cases that have not responded to extensive conservative and interventional treatments. The most common surgical option is minimally invasive sacroiliac joint fusion (arthrodesis). This procedure involves inserting implants or bone grafts across the joint to eliminate motion. Fusion significantly reduces chronic pain, and patients considered for this procedure usually showed a substantial positive response to the diagnostic anesthetic injection.