Understanding Enthesitis: Why Tendon and Ligament Pain Matters in Spondyloarthritis
At EULAR 2025, Tiffany attended a session on “What’s Really Causing Enthesitis – and Why it Matters.” Enthesitis is a major source of pain and disability for people living with spondyloarthritis conditions like axial spondyloarthritis and psoriatic arthritis. While joints often get most of the attention, many patients know that the pain they feel most intensely does not always come from the joint itself. Instead, it comes from the places where tendons and ligaments attach to bone. These attachment points are called entheses, and when they become inflamed, the condition is known as enthesitis.
This session explored what may trigger enthesitis, how it spreads inflammation through the body, and why understanding these pathways could lead to better diagnosis and more targeted treatment.
In this Go With Us! video from EULAR 2025, Tiffany Westrich-Robertson—person living with axial spondyloarthritis and CEO of AiArthritis—shares important updates about enthesitis, a common and painful symptom in spondyloarthritis and psoriatic arthritis.
What exactly is enthesitis?
Enthesitis is inflammation at the point where tendons or ligaments connect to bone. These areas are under constant mechanical stress, which makes them especially vulnerable in inflammatory diseases. For people with spondyloarthritis, enthesitis can cause deep, persistent pain that is often mistaken for muscle strain or overuse injuries.
What makes enthesitis especially important is its location. Entheses sit right next to synovial tissue and bone. When inflammation starts here, it does not always stay localized. Over time, it can spread.
How enthesitis can drive joint and bone damage
The session highlighted that enthesitis may play a central role in how damage develops in spondyloarthritis.
The inflammatory process can follow a cycle:
- Inflammation begins at the entheses
- That inflammation spreads into nearby synovial tissue
- Synovial inflammation contributes to joint damage
- Ongoing inflammation can also affect the bone itself
This helps explain why some people experience significant pain and structural changes even when joint swelling does not seem severe at first. It also shifts how researchers think about where disease activity truly begins.
The gut, the skin, and inflammation pathways
Researchers have long studied the gut as a possible starting point for inflammation in psoriatic arthritis. Around 60 percent of people with psoriatic arthritis have some level of gut inflammation, even if they do not have a formal gastrointestinal diagnosis. This gut inflammation may act as an environmental trigger that sets the immune system in motion.
The session also explored another important pathway: the skin.
About 80 percent of people with psoriatic arthritis experience psoriasis at some point. Immune cells, particularly T cells, are active within psoriasis skin lesions. Researchers are studying how inflammation in the skin may cross biological barriers and contribute to inflammation at the entheses.
This creates a possible chain reaction:
- Immune activity in psoriasis skin lesions
- Spread of inflammatory signals beyond the skin
- Activation of inflammation at the entheses
- Progression to synovial and bone involvement
Understanding this sequence could help explain why skin symptoms and tendon pain are so closely linked in psoriatic arthritis.
Why this matters for diagnosis and treatment
One of the most exciting implications of this research is the potential to improve both diagnosis and treatment matching.
Enthesitis can look very similar to mechanical injury or overuse. Differentiating inflammatory enthesitis from sports injuries or repetitive strain is critical. When enthesitis is clearly driven by disease rather than mechanics, and especially when it occurs alongside psoriasis, it may help clinicians recognize psoriatic arthritis earlier.
It may also guide treatment decisions. If certain inflammatory pathways are more active in a person’s disease, that information could help determine which medications are more likely to work for them, such as choosing one biologic class over another.
A growing focus in spondyloarthritis research
Enthesitis has become a major focus at rheumatology conferences in recent years, and this session reinforced why. By shifting attention to where inflammation starts and how it spreads, researchers are uncovering new ways to understand pain, prevent damage, and personalize care.
For patients, this growing focus is encouraging. It validates the real pain experienced outside of the joints and signals that research is moving closer to addressing the full picture of spondyloarthritis, not just what shows up on traditional imaging or lab tests.
As research continues, better tools for detecting enthesitis and understanding its drivers may lead to earlier diagnosis, more effective treatment strategies, and improved quality of life for people living with these complex diseases.
Discover innovation and collaboration at the AiArthritis Go With Us Conferences Program, where patients and experts share knowledge to advance healthcare journeys and advocacy.
