Pain and swelling outside a joint Is it enthesitis ?

Certain new concepts in joint disease are gradually being introduced and treated. One such painful condition is named ‘enthesitis’. Although not exactly a type of ‘arthritis’, enthesitis could be troublesome as any other disease of the joints. Here is a simple introduction to a condition that could make certain body parts around a joint quite painful and swollen.

What is enthesitis?
Before I explain this term I would like to describe what an ‘enthesis’ is. Enthesis is an attachment site of a muscle to a bone, a ligament to a bone or a joint covering (capsule) to a bone. Therefore an enthesis should be close to a bone at all times. As you know muscle is a structure which contracts and makes your body parts move. Muscles are attached to bone and the point of attachment is called an enthesis. Ligaments are structures which hold two bones close to each other. 

They are like tight rubber bands. The site of attachment of ligaments to bones are also called enthesis. A joint covering/capsule is a protective structure that surrounds joints. This structure is annexed to bones through an enthesis.

If these enthesis become inflamed/swollen we call this enthesitis. The exact reason for enthesitis is unknown but sometimes this is associated with arthritis.

What are the common types of enthesitis?
When the outer aspect of the elbow becomes swollen we call this “tennis elbow”. Similarly the swollen inner aspect of the elbow is called a “golfer’s elbow”. Both conditions are types of enthesitis where the actual elbow joint is not affected. The forearm muscles that attach themselves to the elbow joint become swollen and painful to touch. 

The heel and the ankle could get affected by enthesitis as well. At the bottom of the heel, a structure named plantar fascia can get inflamed/swollen. Plantar fascia is a ligament. It acts like a tense rubber band and helps your foot to absorb shock waves. This painful condition at the bottom of your heel is called “plantar fasciitis”. Behind the ankle lies a huge structure termed achilles tendon. This tendon can swell up and give rise to severe symptoms. Then we name it as “achilles tendinitis”.

Enthesitis is even felt close to the knee joints as well. There are several strong ligaments which stabilize the knee. These get swollen and create symptoms that sometimes mimic knee joint pain.

When arthritis affects the spine, it is named as spondyloarthritis. Spondyloarthritis affects not just the spine but even the structures mentioned above. So as a routine we check for a bit of heel pain, elbow or knee pain in patients who have spondyloarthritis. 

How do we acquire enthesitis?
As medical professionals it is difficult to identify an exact trigger for enthesitis. As mentioned above spondyloarthritis can erupt in combination with enthesitis. But we often see healthy people presenting with mild varieties of enthesitis like tennis elbow, achilles tendinitis or plantar fasciitis. The underlying cause is not identified in many instances and mostly enthesitis is a self-limiting illness.

What are the ways of evaluating and treating enthesitis?
The joint disease specialists will examine the patients and come to a judgement on whether they have enthesitis. Usually blood tests or imaging modalities like X rays are not useful. If the spine is involved in combination with enthesitis certain special blood tests and MRI scans are useful to come to a conclusion. In most instances enthesitis is a diagnosis done by the consultant after a thorough examination.

For a simple tennis or golfers elbow, advice on positioning the forearm and using the hand is useful. Pain relief can be obtained by drugs like NSAIDS or steroids. If these fail, injections are used. Even for heel pain/ plantar fasciitis, advice on footwear and stretching exercises are extremely useful. 

If several parts of the body are affected by enthesitis with joint involvement, disease modifying drugs are carefully utilized. 

As mentioned above, spondyloarthritis is swelling of the joints within the spine. Spondyloarthritis can present with enthesitis and is treated with disease modifying drugs or a special category of medication termed biologics. 

The doctor will guide a physiotherapist to help the patient with symptoms of enthesitis. Ultrasound therapy, heat therapy and stretching are useful to bring down the pain.

(The writer is a consultant in Joint disease, Rheumatology and Rehabilitation and a Member of American College of Rheumatology)