MS vs. Sacroiliitis: What Are the Differences?

Although both multiple sclerosis (MS) and sacroiliitis can cause lower back or hip pain, they are otherwise unrelated conditions that differ significantly in biology, diagnosis, and treatment.

MS is an autoimmune disease of the brain and spinal cord. Pain in MS is related to either nerve damage or muscle/soft tissue damage that occurs as people with MS try to manage certain MS symptoms like spasticity (muscle stiffness and tightness), numbness, or imbalance.

Sacroiliitis is inflammation of one or both of the sacroiliac (SI) joints. These large joints are located on each side of the body and connect the lower spine to the hip bone. Various health conditions or issues may cause sacroiliitis, including arthritis, pregnancy, trauma, and infection.

This article will provide a general overview of MS and sacroiliitis and highlight key differences between the two conditions.

Symptoms

Pain in the lower back or hip is a hallmark symptom of sacroiliitis. In MS, lower back/hip pain is not a direct result of the disease but rather a secondary effect of people with MS trying to adapt to their symptoms.

Multiple Sclerosis

MS symptoms arise from interrupted nerve signaling between the brain and spinal cord and the rest of the body.

Pain is a common symptom of MS, and there are two types, which are:

• Neuropathic pain occurs from nerve damage within the brain and spinal cord. An example of neuropathic pain in MS is a tingling or burning sensation in the feet and legs.
• Musculoskeletal pain is muscle/soft tissue damage that develops as a person compensates for their MS symptoms. For example, a person may place more weight on one side of their body to compensate for a weak foot or stiff leg. This abnormal stress could lead to hip or lower back pain.

Other common symptoms of MS include:

• Sensory disturbances like numbness
• Fatigue
  
• Blurry or double vision
• Constipation
• Bladder dysfunction 
  

Sacroiliitis

The main symptom of sacroiliitis is a sharp or aching pain felt in the lower back, hip, and/or buttock. The severity of sacroiliitis pain depends on the degree of inflammation or injury to the joint.

Besides pain, other symptoms of sacroiliitis may include:

• Radiation or movement of the pain to the leg, groin, or lower abdomen
• Stiffness in the lower back/hip/buttock upon awakening or after sitting for a long time
• Pain and stiffness that are relieved with physical activity
• Whole-body (systemic) symptoms like fever or weight loss

Causes

MS is an autoimmune condition, and sacroiliitis may be caused by or associated with certain autoimmune conditions. Apart from this general similarity, MS and sacroiliitis are vastly distinct conditions.

Multiple Sclerosis

MS occurs when the immune system malfunctions and attacks nerve fibers and their protective myelin covering in the brain and spinal cord.

Experts do not know why the immune system launches such misguided attacks in MS. It's likely that a combination of factors, both genetic and environmental, are involved.

Some environmental factors potentially linked to MS development include:

• Vitamin D deficiency
• Smoking
• Prior infection with the Epstein-Barr virus (EBV)

Sacroiliitis

The purpose of your SI joints is to facilitate absorption and transmission of any impact from your spine to the lower part of your body.

Inflammation of the sacroiliac joint may be caused by a variety of health conditions or factors.

Some of these conditions and factors are:

• Ankylosing spondylitis (AS): This is a chronic autoimmune arthritis in which your immune system attacks your spine and sacroiliac joints.
• Osteoarthritis: This is a noninflammatory type of arthritis that can cause degeneration (wear and tear) of the SI joint.
  
• Trauma: Any injury (e.g., car accident or heavy lifting) that affects the lower back, hip, or buttocks may inflame the SI joint.
• Pregnancy: Increased production of the pregnancy hormone relaxin makes the SI joint less stable and prone to injury. Also, the added weight of pregnancy can cause wear on the SI joint.
• Infection: Rarely, bacteria can seed and infect the SI joint. This may be associated with pelvic trauma, intravenous (I)V drug use, or a urinary tract infection (UTI).
  

Diagnosis

There is no single test that can diagnose MS or sacroiliitis. Instead, healthcare providers pool data from a person's medical history, physical exam, and various tests to make the diagnosis.

Multiple Sclerosis

A neurologist, which is a doctor that specializes in diseases of the nervous system, diagnoses MS by reviewing a person's symptoms and performing neurological exam. Results from one or more of the following tests is also considered:

• A magnetic resonance imaging (MRI) of the brain and/or spinal cord
  
• A spinal tap (lumbar puncture)
• Evoked potential tests (measure the electrical activity in the brain)
• Laboratory tests to rule out conditions with overlapping symptoms (e.g., vitamin B12 deficiency, Lyme disease, a bacterial infection caused by a tick bite)

Sacroiliitis

Sacroiliitis typically is diagnosed by a primary care provider, rheumatologist, physiatrist, or orthopedic surgeon using some combination of the following diagnostic tools and tests:

• A musculoskeletal exam, in which your provider will inspect your spine, hip, and sacroiliac joints by pressing on and moving them
• Imaging tests, like an X-ray or magnetic resonance imaging (MRI) of the pelvis/SI joint
• Sacroiliac joint injection, in which your provider injects an anesthetic (numbing medicine) into the joint to see if the pain is relieved
• Various blood tests, like HLA-B27 (a protein found in a large percentage of people with AS)

Treatment

No cure yet has been found for MS. Sacroiliitis, on the other hand, may be reversed, depending on the underlying cause.

Multiple Sclerosis

The treatment of MS usually involves taking a disease-modifying treatment (DMT). DMTs are intended to help reduce MS relapses (flare-ups of symptoms) and slow disease progression.

Since DMTs are "big-picture" drugs, daily MS symptoms like pain, constipation, or spasticity are managed with a combination of lifestyle habits, medications, and rehabilitation therapies.

Specifically, lower back or hip pain in MS is usually treated with physical therapy, and an over-the-counter (OTC) pain medication like Tylenol (acetaminophen) or a nonsteroidal anti-inflammatory drug (NSAID) like Motrin or Advil (ibuprofen). A muscle relaxant like Kemstro (baclofen) may be prescribed if the pain stems from spasticity.

Sacroiliitis

The treatment of sacroiliitis entails two main goals:

• Reducing pain
• Managing the underlying cause/condition

Pain is controlled through a combination of physical therapy and medications, including topical drugs like lidocaine (a numbing agent) and oral drugs like ibuprofen. A corticosteroid injection into the inflamed joint is also sometimes incorporated into the treatment plan.

Radiofrequency ablation (a minimally invasive procedure in which radio waves are used to heat and disrupt nerve function) may be tried if the other treatments don't work.

Joint fusion surgery (when the two bones of the SI joint are connected using a metal device) is generally considered a last resort treatment option for sacroiliitis.

Other treatments may be warranted depending on why a person develops sacroiliitis. For example, an anti-tumor necrosis factor (TNF) may be recommended if sacroiliitis is due to ankylosing spondylitis. Anti-TNF drugs, like Enbrel (etanercept), work to suppress or quiet inflammation in the body.

Prevention

Healthy lifestyle behaviors may be helpful in protecting against or treating MS or sacroiliitis.

Multiple Sclerosis

The following lifestyle habits may help decrease MS disease activity or prevent MS onset in certain individuals:

• Maintaining a healthy weight
  
• Avoiding smoking
• Participating in regular physical activity
• Ensuring a sufficient vitamin D level through sun exposure or supplementation
  

Sacroiliitis

Depending on the underlying cause, certain lifestyle behaviors can help prevent sacroiliitis onset or worsening.

For example, if you are pregnant, avoiding positions that place extra stress on the SI joint (e.g., crossing your legs) can help prevent sacroiliitis.

Likewise, if you have AS, engaging in exercise therapy can help reduce pain and protect against long-term SI joint damage.

Summary

Multiple sclerosis (MS) and sacroiliitis can both cause lower back or hip pain, although through unrelated means. Pain in MS stems directly from nerve damage or indirectly from muscle/soft tissue damage. The pain of sacroiliitis stems from inflammation of the sacroiliac joint.

Apart from the goal of easing pain, the diagnosis and treatment of MS and sacroiliitis are also distinct.

A Word From Verywell

Whether you are experiencing pain from sacroiliitis or MS, it's important to get it checked out by your healthcare provider. Each condition requires a careful assessment and thoughtful discussion about therapy options. As you navigate the challenges of MS or sacroiliitis, practice self-compassion and reach out to loved ones for support.