The sacroiliac (SI) joints are two paired structures located deep in the pelvis, linking the iliac bones to the sacrum, the triangular bone at the base of the spine. Their primary function is to transfer weight and forces between the upper body and the legs, providing shock absorption and stability. Dysfunction in this area, known as sacroiliac joint dysfunction, contributes to lower back and hip pain. This condition arises when the joint experiences either too much motion (hypermobility) or too little motion (hypomobility), leading to inflammation and discomfort.
The Hallmarks of Sacroiliac Pain
Sacroiliac pain is typically described as a deep, aching discomfort localized to the buttock, usually affecting only one side. This pain is often felt at or just below the posterior superior iliac spine (the dimple visible on the lower back). The quality of the pain varies, ranging from a constant, dull ache to sudden, sharp, stabbing episodes.
Pain frequently radiates outward, traveling down the back of the thigh, though it rarely extends below the knee. Pain may also migrate into the groin, hip, or lower abdomen. This radiating pain can sometimes mimic sciatica, causing tingling, numbness, or a shooting sensation.
Specific movements that place shear stress on the joint aggravate the discomfort. Common triggers include the transition from sitting to standing, standing on one leg, climbing stairs, running, or prolonged sitting or standing. Instability can sometimes cause a feeling of the leg buckling or “giving out.”
Common Factors Leading to SI Joint Dysfunction
SI joint dysfunction stems from mechanical stressors that either loosen the joint’s supportive ligaments (hypermobility) or cause the joint to become stiff (hypomobility). Pregnancy and childbirth are frequent causes due to the release of the hormone relaxin, which increases ligament laxity to prepare the pelvis for delivery. Increased weight and altered gait during pregnancy further strain the joint, and this hypermobility may persist postpartum.
Biomechanical imbalances also place uneven stress on the SI joints. Conditions such as a leg length discrepancy, scoliosis, or gait abnormalities force the body to distribute weight unevenly, leading to repetitive forces. Athletes in sports requiring repetitive twisting or asymmetrical loading, like golf or figure skating, are also susceptible.
Other factors include degenerative conditions and acute trauma. Osteoarthritis causes wear and tear on the joint’s cartilage, leading to inflammation (sacroiliitis). Acute trauma, such as a fall onto the buttock or a motor vehicle collision, can directly damage the ligament network. Previous spinal fusion surgery in the lower back can also increase mechanical stress on the adjacent SI joint.
Diagnostic Steps for Confirming SI Pain
Diagnosing SI joint pain is challenging because its symptoms overlap with conditions like lumbar disc issues or hip arthritis. The clinical assessment begins with a physical examination where a healthcare provider performs specific provocative tests to isolate the joint as the source of pain. These maneuvers, including the Distraction, Thigh Thrust, and Patrick’s (FABER) tests, are designed to stress the SI joint. A positive response occurs if the maneuver reproduces the patient’s typical pain.
Imaging studies, such as X-rays or MRI scans, are often used to rule out other conditions like fractures or severe lumbar spine pathology. Standard imaging, however, does not reliably confirm SI joint dysfunction, as structural changes visible on a scan may not correlate with pain.
The most accurate method for confirming the diagnosis is a fluoroscopically guided diagnostic injection. During this procedure, a local anesthetic is injected directly into the joint under real-time imaging guidance. If the patient experiences a reduction in pain (typically more than 50% relief) within a short time, it confirms the SI joint is the source of the discomfort.
Initial Management Strategies
Initial treatment focuses on conservative, non-surgical methods aimed at reducing inflammation and restoring stability. Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to manage acute pain and swelling. For localized relief, ice application during the initial 48 hours helps reduce inflammation, while heat therapy can relax surrounding muscles later.
Physical therapy is a primary treatment concentrating on stabilizing the core and the pelvis. A targeted rehabilitation program involves strengthening the gluteal muscles and hip stabilizers, which provide dynamic support for the joint. Correcting muscle imbalances and improving posture are also addressed to reduce uneven stress on the pelvic girdle.
For patients with hypermobility, especially those with pregnancy-related dysfunction, a pelvic or SI joint belt can provide temporary external support. If conservative measures fail, interventional treatments may be considered. Corticosteroid injections, delivered into the joint, offer temporary pain relief by decreasing inflammation, allowing the patient to participate fully in physical therapy.