Inflammatory Arthritis: Types of Active Inflammation

Active inflammation of the sacroiliac joints is a key feature of sacroiliitis and spondylitis, which are forms of inflammatory arthritis that affect the spine.

It can take many years from when you first notice symptoms to when you finally get a spondylitis diagnosis. The average length of time is seven to eight years.


First, it's important to see a specialist such as a rheumatologist as soon as you can when you have active inflammation symptoms. Rheumatologists are trained to detect, diagnose and treat this type of back pain.

Second, most types of healthcare providers, particularly primary care doctors, struggle to recognize inflammatory back pain. This is especially so when it comes to distinguishing it from mechanical back pain.

Another thing that makes getting a diagnosis for inflammatory arthritis difficult is that it can take a long time for telltale changes in your sacroiliac joint to show up on x-rays. Luckily, new MRI technology makes it much easier to spot. In fact, MRIs can identify four types of active inflammation that may be present in spondylitis. Below are the descriptions.



Sacroiliac and low back pain
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Osteitis is an inflammation of bone tissue caused by infection, degenerative changes or trauma. Osteitis results in edema, or swelling, of the adjacent bone marrow. Osteitis is associated with ankylosing spondylitis.

Symptoms of osteitis include are similar to any type of inflammation and include pain, and occasionally redness and swelling of the overlying skin.

When talking about sacroiliitis and spondyloarthritis it may be important to note that, first, signs of osteitis on an MRI likely definitively indicates that you have these bony changes, and that second, there is an early stage osteitis and a late stage osteitis.  

The characteristics of osteitis at the sacroiliac joints are very different at each stage.  Of course, it's important to catch the signs early so that you give your treatment the best possible chance to work for you and help you manage the pain and/or disability.



Enthesopathy X-Ray
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Enthesitis is inflammation of soft tissue (muscle, ligament or tendon) where it inserts into the bone. It is associated with arthritis and is one of the main signs of spondyloarthritis (arthritis that affects the spine.)

That said, enthesitis is generally felt in the heels and sometimes the knees, although it can lead to swelling and soreness in the upper body and/or pelvis, as well. Enthesitis is related to diffuse idiopathic skeletal hyperostosis (acronym DISH) which is a condition related to aging in which spinal ligaments harden. It may also occur along with diseases such as systemic lupus erythematous or sarcoidosis. 

Enthesitis often causes the affected area of the soft tissue to become ropey (called fibrosis) and/or solid (called calcification or ossification). It can be quite painful; the pain occurs mainly when you use your muscles and they pull on your bones.



A doctor holds a model of the spine and points to a structure.
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Capsulitis is inflammation of any anatomical capsule. In the body, an anatomical capsule is a structure, generally made of fibrous tissue, that encases a part or parts. For example, the facet joints at the back of the spinal column are enclosed in capsules known aptly as facet joint capsules. Perhaps the most well-known form of capsulitis is adhesive capsulitis, or frozen shoulder, but in the spine, the facet joints are the most affected by this form of inflammation.



Artists depiction of active inflammation at the sacroiliac joints.
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Synovitis is inflammation of any synovial membrane of a joint. Synovial membranes line joint capsules, and secrete synovial fluid to nourish cartilage and lubricate the joint.

Synovitis is common in arthritis. Symptoms may include pain when you move the affected part and swelling. If you have synovitis, your healthcare provider may suggest or prescribe NSAIDs to control the inflammation and pain. 

By Anne Asher, CPT
Anne Asher, ACE-certified personal trainer, health coach, and orthopedic exercise specialist, is a back and neck pain expert.