Anatomy of Sacroiliac Joint and Basic Understanding of Sacroiliitis

Sacroiliac joints connect the pelvic ilium and vertebral column sacrum. This strong, weight-bearing joint transfers lower limb forces to the vertebral column. One or both sacroiliac joints are painfully affected by sacroiliitis. The pelvis and lower spine meet at these joints. Sacroiliitis may induce pain and stiffness in the buttocks and lower back, potentially radiating to the legs. Standing or sitting for long periods or climbing stairs can worsen the pain.

Sacroiliac Joint 

The joint capsule and inner membrane make the SI joint synovial and diarthrodial, meaning moveable. The sacroiliac joint possesses a fibrous capsule anteriorly but lacks one posteriorly. For this reason, some researchers call the sacroiliac joint an atypical synovial joint or modified synarthrodial joint.  

Articular Surfaces

The sacrum and ilium's auricular surfaces form the synovial sacroiliac joint. Despite being a synovial plane joint, the sacroiliac joint's auricular surfaces have depressions and elevations. The central sacral concavity matches the iliac convexity, interlocking the two auricular surfaces and providing stability. The ilium and sacrum have fibrocartilage and hyaline cartilage, respectively, on their auricular surfaces.

The sacroiliac joint is synovial on its anterior side and a syndesmosis on its posterior side between the sacrum and ilium tuberosities, according to some authors. In a syndesmosis, fibrous connective tissue forms an interosseous membrane to join bones.

Movements

Sacroiliac joint movement is limited by its arrangement and strong ligaments. The sacroiliac ligament, like other plane-type synovial joints, allows only limited gliding and rotation. Nutation and counternutation are two ways that the sacroiliac joint can turn.

• Nutation: It occurs when the superior sacrum tilts downward and anteriorly and the inferior sacrum and coccyx tilted posteriorly. Sacral flexion occurs only with trunk flexion or hip extension.

• Counternutation: It occurs when the superior sacrum tilts upwards and posteriorly while the inferior sacrum and coccyx tilt anteriorly. Sacral extension occurs only with trunk extension or hip flexion.

The sacroiliac joint is one of the pelvic mechanism's pillars, transmitting head, trunk, and upper limb weight to the lower limbs. Sacroiliac joint immobility promotes strength and stability for weight bearing. To stay upright while standing or walking, these traits are crucial. The hormone relaxin loosens the joints and ligaments during childbirth, allowing more mobility. To accommodate the fetus, the sacroiliac joints are counternutation to increase pelvic inlet and outlet diameters.

What is Sacroiliitis?

The sacroiliac joint—where your spine meets your pelvis—inflames painfully. It hurts your lower back, buttocks, or legs. Two bones meet at a joint. The sacroiliac joints connect the spine and pelvis. The sacrum is the triangle-shaped last part of your spine. The ilium is the top of your pelvis. When you move your hips, you use your sacroiliac joints, some of the largest in your body. Sacroiliitis occurs when your sacroiliac joints are irritated or damaged. Inflammation from irritation causes low back and buttock pain. Visit a doctor for low back pain. This common symptom can be caused by many things. If a pain doctor in Dallas diagnoses your pain quickly, you can treat it and reduce its impact on your daily life.

Pain and Discomfort from Sacroiliac Joint Variations

Sacroiliac joint anatomy varies in 3% to 50% of the population. Variants may involve 

• Cartilage, ligament, or bone structural changes. 

• Sacroiliac accessory joint

• Iliosacral

• Bipartite iliac bone

• Crescent-shaped bone

Most symptoms occur in the accessory sacroiliac joint, which degenerates. Because it bears weight all the time and has a unique shape, the sacroiliac joint(s) can be painful. Joint symptoms can result from cartilage, bone, or ligament damage. The sensitive nerve network around the joint can send painful signals.

Symptoms

Lower back pain is the most common sacroiliitis symptom. The pain might get worse after standing or sitting for a long time and also worsen with hip rotation.  You may feel sudden stabby pain. A constant dull ache may also occur. Stretch from your lower back to your buttocks, hips, or thighs. Sacroiliitis causes morning stiffness. After sleeping or sitting, stiffness is normal, but sacroiliitis causes stiffness that lasts more than an hour every morning.

Causes

Causes of sacroiliac joint problems:

• Injury:  A car accident or fall can damage the sacroiliac joints.

• Arthritis: Sacroiliac joint pain can develop osteoarthritis. Spinal arthritis, ankylosing spondylitis, can too.

• Pregnancy: Childbirth loosens and stretches sacroiliac joints. Weight gain and walking differently during pregnancy can strain these joints.

• Infection:  Infections of the sacroiliac joint are rare.

Management and Treatment

• The most common joint pain relief treatment is physical therapy. Your sacroiliac muscles will be strengthened by physical therapy stretches and exercises. This will stabilize your joints by relieving pressure. Sacroiliitis exercises increase sacroiliac joint range of motion.

• Medication for pain management may be suggested by your doctor. Over-the-counter NSAIDs include aspirin, ibuprofen, and naproxen. Do not take NSAIDs for more than 10 days without consulting a Dallas pain clinic. Prescription muscle relaxers (muscle relaxants) block nerve pain signals to the brain to treat muscle pain. Prescription corticosteroids relieve pain and inflammation. Your doctor may inject a corticosteroid into your joint. Corticosteroid injection is one of the best joint pain relief treatments. 

• Radiofrequency ablation (RFA) to permanently block joint nerves from sending pain signals to your brain is rare, but your doctor may recommend it.

• Rheumatologists of Premier Pain Centers who treat inflammatory diseases, can help you to treat sacroiliac joints.

• Surgery for sacroiliitis is rare. Physical therapy and RFA may not help your pain, so your joint pain specialist in Dallas may recommend surgery. Your surgeon may fuse the joint with surgical screws. They'll explain your procedure and recovery.

Conclusion