What Is Enthesitis? Symptoms, Causes, Diagnosis, and Treatment

Enthesitis is inflammation of the entheses, the area where ligaments or tendons connect to your bones. About half of all people with psoriatic arthritis experience enthesitis, according to the National Psoriasis Foundation.

Areas of the body where enthesitis commonly occurs in people with psoriatic arthritis include the feet and lower legs, as well as areas around the ribs, spine, and hips. Enthesitis can cause joint pain or stiffness, especially when you move — potentially leading to problems with mobility, as noted by the Arthritis Foundation.

The patterns of enthesitis seen in psoriatic arthritis — potentially affecting multiple areas of your torso, hip area, and feet — are not seen in any other form of arthritis. For this reason, enthesitis is often used to help diagnose psoriatic arthritis and rule out other related conditions.

It’s important for your doctor to take enthesitis into account when prescribing and evaluating treatments for psoriatic arthritis. Over time, enthesitis can make the affected areas become damaged and less flexible (known as fibrosis) or even completely solid (known as calcification).

Enthesitis tends to cause pain and stiffness in the affected areas of your body. In people with psoriatic arthritis, enthesitis most commonly occurs in the following areas where ligaments or tendons connect to bone, the National Psoriasis Foundation notes:

Bottom of foot
Achilles tendon (back of lower leg)
Ribs
Spine
Pelvis

While the areas listed above are the most common sites of enthesitis in psoriatic arthritis, any of the more than 100 entheses in your body can be affected, the Arthritis Foundation notes.

Over time, the inflammation in enthesitis can lead to abnormal bone growth, leading to bone spurs — growths that project out from the edges of bones. While some bone spurs cause no symptoms, others may cause pain or discomfort or reduce the range of motion in a joint, Mayo Clinic notes.

In some cases of enthesitis, long-term tissue damage can lead to hardening of the affected tissues. When the tissues become less flexible, this is known as fibrosis, and when tissues completely harden, it’s known as calcification (or ossification). Both conditions can contribute to joint stiffness.

In people with psoriatic arthritis, enthesitis is often linked to changes in your fingernails and toenails such as pitting or separation from the nail bed, according to the Arthritis Foundation. The reasons for this link are unclear.

Enthesitis occurs when an enthesis becomes inflamed. This may occur when physical stress on the area leads to microscopic damage, and your immune system responds by releasing proteins that cause inflammation, the Arthritis Foundation notes.

While physical stress on a joint may cause enthesitis in someone who doesn’t have psoriatic arthritis, it’s far more likely to occur in someone who does have psoriatic arthritis, and it can occur due to normal use, research shows.

Outside the context of psoriatic arthritis, enthesitis often occurs due to overuse of a joint — for example, it’s often seen in tennis elbow. In these cases, enthesitis tends to get better as part of the normal healing process. But in psoriatic arthritis, enthesitis tends to be ongoing and doesn’t get better with measures like resting the joint or applying an ice pack.

In addition to psoriatic arthritis, conditions that can cause enthesitis include:

Overuse injury
Spondyloarthritis (including ankylosing spondylitis)
Reactive arthritis

In most cases, there’s no need to have a formal or detailed diagnosis of enthesitis when it affects someone with psoriatic arthritis. Your doctor will note that you’re probably experiencing enthesitis based on your medical history, the symptoms you report, and a physical exam. In some cases, your doctor may press against a tendon to see if it causes pain or tenderness as a way to help confirm enthesitis.

Right now, there is no consensus about the best way to define or score the severity of enthesitis using imaging tests, a review article notes.

But your doctor may order any of the following imaging tests to get a more detailed look at your enthesitis:

Research is ongoing into the most effective treatment of enthesitis in people with psoriatic arthritis.

In a research study, researchers compared the effectiveness of NSAIDs, conventional disease-modifying antirheumatic drugs (DMARDs), and biologic drugs in relieving enthesitis in a group of 526 participants with psoriatic arthritis. They found that 453 (86.1 percent) experienced complete resolution of their enthesitis over an average duration of 8.73 months, and that a similar rate of resolution was seen regardless of which of the three types of drugs the participants took.

But according to reporting by the Arthritis Foundation, enthesitis often does not respond well to conventional DMARDs commonly used to treat psoriatic arthritis, such as methotrexate and leflunomide.

Instead, as a first step, your doctor may prescribe a high dose of a nonsteroidal anti-inflammatory drug (NSAID) such as naproxen or indomethacin. But high doses of these drugs can only be taken for up to about a month, and they’re not an option for many people, such as those with a history of certain gastrointestinal problems like ulcers.

If you have enthesitis in only one location, your doctor may inject a steroid in the area to help reduce inflammation.

If you have enthesitis in multiple locations, you may need to take a biologic drug, such as a TNF inhibitor, for long-term treatment.

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