Enthesitis in Spondyloarthritis vs Mechanical Enthesopathy: Ultrasound Differentiation and the OMERACT Approach
Ultrasound Semiotics of Inflammatory Enthesitis
According to Jacobson (Fundamentals of Musculoskeletal Ultrasound, 2026), in spondyloarthropathies such as psoriatic arthritis, sonography can demonstrate peritendinal inflammation as well as inflammatory enthesitis at tendon attachment sites. It is characterized by the following features:
- abnormal hypoechogenicity;
- hyperemia;
- erosions;
- enthesophytes.
Differentiation of Inflammatory and Degenerative Enthesophytes
The key point in differential diagnosis is the characterization of the enthesophyte. According to Jacobson (2026), correlation with radiography helps distinguish between degenerative and inflammatory enthesophytes: inflammatory enthesophytes are ill-defined. Thus, B-mode and Doppler describe the activity of the process (hypoechogenicity, hyperemia), while radiography clarifies the morphology of bone changes.
| Feature | Inflammatory Enthesitis (SpA) | Mechanical/Degenerative Enthesopathy |
|---|---|---|
| Echogenicity of enthesis | Abnormal hypoechogenicity | [to be clarified] |
| Hyperemia (Doppler) | Present | [to be clarified] |
| Erosions | Present | [to be clarified] |
| Enthesophyte | Ill-defined | Well-defined (on radiography) |
Role of the OMERACT Approach
OMERACT (Outcome Measures in Rheumatology) is an international initiative for standardizing outcome measures in rheumatology. Regarding ultrasound definition of enthesitis in spondyloarthritis, the work of Terslev L, Naredo E, Iagnocco A et al., "Defining enthesitis in spondyloarthritis by ultrasound: results of a Delphi process and of a reliability reading exercise" (Arthritis Care Res, 2014), cited in EFSUMB Guidelines (Part I, 2022), is significant. Detailed consensus criteria are not provided in the available fragments [to be clarified].
Note on Conclusion Formulation
According to ultrasound methodology, it is correct to describe what is actually visualized in B-mode and during Doppler interrogation (hypoechogenicity, hyperemia, erosions, enthesophytes), and to correlate morphological interpretation with radiography and the clinical-serological context. The application of OMERACT semi-quantitative scales is oriented primarily toward research context and structured monitoring over time.
Frequently asked questions
What are the ultrasound signs indicating inflammatory enthesitis in spondyloarthritis?
According to Jacobson (2026): abnormal hypoechogenicity, hyperemia, erosions, and enthesophytes at tendon attachment sites, as well as peritendinal inflammation.
How can inflammatory enthesophytes be distinguished from degenerative ones?
Correlation with radiography helps: inflammatory enthesophytes are ill-defined, degenerative ones are well-defined (Jacobson, 2026).
Is there an OMERACT ultrasound definition of enthesitis for spondyloarthritis?
Yes, it was developed as part of a Delphi process: Terslev, Naredo, Iagnocco et al., Arthritis Care Res 2014. The details of the criteria are not provided in the available fragments [to be clarified].
Is it mandatory to apply OMERACT grading in routine ultrasound reports?
No. OMERACT semi-quantitative scales are used primarily in scientific research and structured monitoring over time, not as a mandatory requirement for routine practice.