Things worth knowing about "SI joint"
The SI joint (sacroiliac joint) connects the pelvis to the spine. Pain in this area is common and can result from joint dysfunction, inflammation, or degenerative changes.
What is the SI Joint?
The SI joint, or sacroiliac joint, is the paired joint connecting the ilium (hip bone) to the sacrum (tailbone region). Located in the lower back on either side of the spine, it forms a key part of the pelvic girdle. The SI joint transfers forces between the upper body and the legs, providing stability during walking, standing, and sitting. Unlike most joints in the body, the sacroiliac joint has very limited range of motion and is classified as an amphiarthrosis (a slightly movable joint).
Anatomy of the SI Joint
The SI joint is surrounded by a strong network of ligaments that ensure its stability. Key structures include:
- Anterior sacroiliac ligament
- Posterior sacroiliac ligament
- Iliolumbar ligament
The joint surfaces are covered with cartilage and enclosed in a joint capsule. With advancing age, the SI joint may undergo partial or complete fusion (ankylosis), naturally reducing its mobility.
Causes of SI Joint Problems
Pain and dysfunction of the SI joint can have various causes:
- SI Joint Dysfunction (Blockade): A functional restriction in which the joint becomes locked in an abnormal position, one of the most frequent causes of low back pain.
- Sacroiliitis: Inflammation of the SI joint, often associated with rheumatic conditions such as Ankylosing Spondylitis (Morbus Bechterew) or other spondyloarthropathies.
- Osteoarthritis (Degeneration): Wear and tear of the joint cartilage due to overuse, poor posture, or previous injury.
- Trauma: Falls or accidents can directly injure the SI joint or cause lasting instability.
- Pregnancy: The hormone relaxin loosens the ligaments of the pelvis, increasing SI joint mobility and potentially causing pain.
- Leg length discrepancy: Unequal leg lengths can place uneven stress on the SI joint, leading to pain on one side.
Symptoms of SI Joint Disorders
SI joint symptoms are diverse and are often confused with other causes of back pain. Common complaints include:
- Deep-seated lower back pain, often on one side
- Pain in the buttocks and hip, which may radiate into the leg
- Morning stiffness and start-up pain
- Pain when climbing stairs, standing for long periods, or sitting
- Pain when turning over in bed or rising from a seated position
- In inflammatory cases: night pain and general symptoms such as fatigue
Diagnosis
Diagnosis of SI joint problems is based on a combination of clinical examination and imaging studies:
Clinical Tests
- Mennell Sign: Pain provocation through targeted SI joint movement
- FABER Test (Flexion, Abduction, External Rotation): Assessing hip and SI joint function
- Gaenslen Test: Provocation test for the SI joint through hip hyperextension
Imaging Studies
- X-ray: Visualization of degenerative changes or bony fusion
- MRI (Magnetic Resonance Imaging): Particularly useful for detecting early-stage inflammation (sacroiliitis)
- CT (Computed Tomography): Detailed imaging of bony changes
- Diagnostic Injection: Injection of a local anesthetic into the SI joint can help confirm the source of pain
Treatment of SI Joint Problems
Treatment depends on the underlying cause and may be conservative or interventional:
Conservative Treatment
- Physical Therapy: Targeted exercises to strengthen core and pelvic muscles, and manual therapy to release joint blockades
- Manual Medicine / Chiropractic Care: Specific manipulations to resolve SI joint dysfunction
- Pain Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or diclofenac for pain relief and inflammation reduction
- Heat or Cold Therapy: Supportive measures to relieve acute or chronic pain
- Orthopedic Aids: Pelvic support belts or insoles to offload and stabilize the SI joint
Interventional Treatment
- Corticosteroid Injection: Injection of corticosteroids directly into the joint to reduce inflammation
- Radiofrequency Ablation: Ablation of pain-conducting nerves around the SI joint for chronic pain management
- SI Joint Fusion (Surgical Stabilization): In severe, therapy-resistant cases, the SI joint may be surgically fused (arthrodesis)
Prevention
The following measures can help prevent overloading and early degeneration of the SI joint:
- Regular physical activity and strengthening exercises for the core and pelvic muscles
- Ergonomic posture at work and in daily life
- Weight management to reduce mechanical stress on the joint
- Avoiding repetitive one-sided loading and poor postural habits
References
- Simopoulos TT, Manchikanti L et al. - A Systematic Evaluation of Prevalence and Diagnostic Accuracy of Sacroiliac Joint Interventions. Pain Physician, 2012.
- Szadek KM et al. - Diagnostic Validity of Criteria for Sacroiliac Joint Pain. Journal of Pain, 2009.
- Cohen SP - Sacroiliac Joint Pain: A Comprehensive Review of Anatomy, Diagnosis, and Treatment. Anesthesia and Analgesia, 2005.