What to know about enthesitis

Enthesitis is the medical term for inflammation of one or more entheses. These are sites at which tendons and ligaments attach to bones.

Enthesitis can cause symptoms such as joint pain and stiffness and problems with mobility. The condition can develop as a result of overuse, injuries, or underlying diseases.

This article describes what enthesitis is, including its symptoms, causes, and diagnosis. We also outline potential treatments and offer advice on when to contact a doctor.

What is enthesitis?

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The skeletal system consists of various components, including bones, tendons, and ligaments. Tendons attach muscles to bones, while ligaments attach bones to other bones. Together, these tissues provide support for the body and allow movement.

An enthesis forms at the point where a tendon or ligament attaches to a bone. There are more than 100 entheses in the human body.

Enthesitis occurs when an enthesis becomes inflamed and painful due to one or more of the following:

• excessive use
• injury
• underlying disease

Symptoms and locations

Enthesitis may cause pain, swelling, and stiffness in the affected enthesis. Although it can affect any of the entheses, it most commonly occurs in entheses in the following areas:

• the backbone
• the hips
• the knees
• the heels
• the undersides of the feet

Physical activity may worsen symptoms of enthesitis. A person may have difficulty running, jogging, or climbing stairs because of the pain.

Prolonged enthesitis may lead to permanent changes that affect body movement and function. One of these possible changes is ossification, which is the formation of new bone tissue. An example is a “heel spur,” which is excess bone that grows from the heel.

Another possible change is fibrosis, a condition in which soft body tissues become thickened and scarred, affecting movement.

Causes

Enthesitis can occur as a result of overuse, injury, or underlying disease.

Overuse

Enthesitis can develop as a result of prolonged stress on the joints. This can occur as a result of the following:

• having overweight or obesity
• playing sports
• performing activities that involve repetitive movements

Injury

Enthesitis can also develop after injury to the tendons, ligaments, and other connective tissue. Examples of these injuries include:

• Achilles tendinitis: An overuse injury of the Achilles tendon, which connects the calf muscle and heel bone.
• Rotator cuff syndrome: An injury or degenerative condition affecting the rotator cuff, which is a group of muscles and tendons that hold the upper arm bone inside the shoulder socket.
• Plantar fasciitis: Inflammation of the planta fascia, which is a ligament that connects the heel bone to the toes.
• Bursitis of the hip: Inflammation of the fluid-filled sacs or “bursa” that cushion the hip joints.

Disease

Enthesitis can happen because of underlying inflammatory diseases and autoimmune disorders, where the immune system attacks tissues within the joints. Examples include:

• Psoriatic arthritis: A type of arthritis that may affect people with the skin condition psoriasis.
• Gout: A type of arthritis in which a buildup of uric acid in the body triggers sudden and severe joint pain.
• Juvenile idiopathic arthritis: Arthritis that affects children and teenagers.
• Ankylosing spondylitis: An inflammatory condition that causes the vertebrae of the spine to fuse together.

Doctors do not know precisely how many people with the above diseases will go on to develop enthesitis.

Diagnosis

To diagnose enthesitis, a doctor will ask about a person’s symptoms and medical history, including whether the person has a family history of the condition. They will also examine the affected areas for signs of swelling and tenderness.

In some cases, a doctor may order medical tests to rule out other conditions such as rheumatoid arthritis. Tests may include:

• blood tests
• ultrasound scans
• MRI scans

Depending on the results of the medical tests, the doctor may refer the person to a rheumatologist for a more in-depth investigation.

Treatment

The treatment for enthesitis depends on several factors, including:

• the cause of the condition
• the symptoms a person experiences
• how long the person has experienced symptoms

One possible treatment option is nonsteroidal anti-inflammatory drugs (NSAIDs). Drugs such as ibuprofen and piroxicam can help ease inflammation and pain.

Another treatment option is steroids. Drugs that can help ease inflammation and alleviate joint pain and stiffness. If enthesitis affects a specific joint, a doctor may recommend a corticosteroid injection into the joint to ease symptoms.

A rheumatologist may recommend biological drugs to treat enthesitis resulting from autoimmune arthritis. Biological drugs are ones that derive from living sources, such as plants and bacteria. These drugs can help slow or prevent inflammation by targeting specific steps in the inflammatory process.

Another treatment option is disease-modifying antirheumatic drugs (DMARDs). These drugs help slow the progression of autoimmune arthritis by targeting parts of the immune system itself.

A person may also benefit from the following:

• resting the affected joints
• avoiding activities that worsen symptoms
• practicing physiotherapy to help restore usual joint function and mobility

When to consult a doctor

A person should contact a doctor if they experience any of the following symptoms in their joints:

• pain or discomfort
• warmth
• swelling
• stiffness

It is important that people seek medical attention as soon as enthesitis symptoms develop. Prolonged and untreated enthesitis can cause severe and lasting joint damage that can affect movement.

People who have preexisting inflammatory conditions, such as psoriatic arthritis or ankylosing spondylitis, may worry that enthesitis symptoms signal a worsening of their disease. But enthesitis can occur with both mild and severe forms of these diseases. Having enthesitis symptoms only indicates that the underlying disease is active, and not necessarily that it is worsening.

Summary

Enthesitis is the medical term for inflammation of one or more entheses. These are sites at which connective tissues such as tendons or ligaments attach to bones.

Enthesitis typically causes pain and stiffness of affected joints. The condition can develop in any of the entheses. Common sites include the backbone, hip, knee, heel, and the underneath of the foot.

Treatments are available to help alleviate joint pain, inflammation, and stiffness. Without treatment, enthesitis can cause lasting mobility impairments. Because of this, a person should contact a doctor if they experience concerning symptoms, particularly if they have an underlying condition that increases their risk for developing enthesitis.