MASEI Ultrasound: How Doppler evaluates enthesitis and spondyloarthritis
Author and medical reviewer: Dr. Patrick Felipe Catricala — CRM-SP 133.006 | RQE 46.844 Specialty: Radiology and Diagnostic Imaging Last updated: July 16, 2026
The MASEI — Madrid Sonographic Enthesis Index — is a standardized ultrasound assessment system for entheses , the regions where tendons, ligaments, or fascia insert into bone. The protocol bilaterally examines six groups of insertions and records structural changes, such as calcifications and erosions, as well as possible signs of inflammatory activity, especially vascularization identified by Doppler.
MASEI ultrasound is used as a complementary examination in the investigation of enthesitis and diseases within the spondyloarthritis spectrum, including psoriatic arthritis and ankylosing spondylitis. It is usually requested by rheumatologists and, depending on the case, by orthopedists, physiatrists, sports medicine physicians, or dermatologists who monitor patients with psoriasis.
The MASEI result does not, in itself, confirm or rule out a rheumatological disease.
Quick definition: MASEI is an ultrasound index that organizes, in a bilateral and standardized manner, the findings into six groups of entheses. The grayscale demonstrates morphological changes, while Doppler investigates vascularization at the insertion, a possible sign of inflammatory activity when interpreted in the appropriate location and context.
MASEI in a few words
What it is: Standardized ultrasound of the entheses with grayscale and Doppler evaluation.
Regions examined: insertions of the triceps, quadriceps, proximal and distal patellar tendons, Achilles tendon, and plantar fascia.
How it's done: all structures are evaluated bilaterally.
What Doppler ultrasound detects: slow blood flow in the enthesis region, which may be related to inflammatory activity.
Main indications: investigation of enthesitis in patients with suspected spondyloarthritis, psoriatic arthritis, or pain in multiple entheses.
Interpretation: the result should be correlated with symptoms, physical examination, laboratory tests and, when necessary, other imaging methods.
What are entheses?
Entheses are regions of transition and load transfer between soft tissues and bone.
The term, in an anatomical sense, includes the insertions of tendons, ligaments, joint capsules, and fascia.
Some examples of entheses are:
The insertion point of the Achilles tendon into the calcaneus (heel bone);
Origin of the plantar fascia in the heel;
Insertions of the patellar tendon into the patella and tibial tuberosity;
insertion of the quadriceps tendon into the patella;
The triceps tendon inserts into the olecranon, in the elbow region.
Because these areas are subjected to repetitive tensile and compressive forces, they can exhibit changes caused by inflammation, aging, sports activity, overload, or degeneration.
For this reason, an ultrasound finding at the enthesis needs to be interpreted within the context of the patient's clinical picture.
What is enthesitis?
Enthesitis is inflammation that involves the enthesis.
It can cause localized pain, sensitivity to pressure, stiffness, and functional limitations. Heels, soles of the feet, knees, and elbows are among the areas that may present symptoms.
Enthesitis is a significant manifestation of spondyloarthritis, a group that includes:
axial spondyloarthritis;
peripheral spondyloarthritis;
ankylosing spondylitis;
psoriatic arthritis.
However, not all pain located over an insertion site indicates rheumatological inflammation.
Tendinopathy, trauma, obesity, sports activity, mechanical overload, and degenerative changes can also cause pain and changes in appearance.
In addition to potentially active signs, ultrasound can demonstrate structural consequences such as enthesophytes, calcifications, and erosions. The presence of these findings alone does not indicate when the alteration arose or what its cause was.
What is the MASEI protocol?
MASEI stands for Madrid Sonographic Enthesis Index.
The index was developed to systematize the ultrasound evaluation of entheses in patients with spondyloarthritis and to allow for standardized comparison of findings.
In the original MASEI publication by Miguel and colleagues , six groups of entheses were examined bilaterally. The score assessed:
thickness;
enthesis structure;
calcifications;
bone erosions;
associated bursae;
signal to the power Doppler.
Some components are given different weights in the scoring calculation.
The original study identified a cutoff point with good performance in that sample. However, this value should not be treated as a universal diagnostic limit.
The original sample was relatively small, and subsequent research has shown that the score can be influenced by factors such as the population studied, age, sex, body mass index, and level of physical activity.
A systematic review on the use of MASEI considered the method viable, reliable, and valid for the study of entheses. The review also identified differences between applications of the index and limitations in the scientific literature.
In practice, scoring helps to organize and document findings. It does not replace the rheumatologist's clinical evaluation or the diagnostic or classification criteria applicable to each disease.
What entities are evaluated in MASEI?
The traditional MASEI protocol examines six groups of entheses, bilaterally, totaling 12 anatomical sites.
The structures evaluated are:
Triceps tendon at its insertion on the olecranon.
Quadriceps tendon at its insertion on the superior pole of the patella.
The proximal patellar tendon or ligament, located at the inferior pole of the patella.
Distal patellar tendon or ligament, located at the anterior tibial tuberosity.
Achilles tendon at its insertion into the calcaneus.
Plantar fascia originates near the calcaneus (heel bone).
A complementary ultrasound evaluation may include other structures related to the patient's symptoms.
However, these additional structures should be described separately and not improperly incorporated into the standardized MASEI scoring.
What is analyzed in each enthesis?
The examiner combines morphological changes demonstrated in grayscale with the investigation of vascularization using Doppler.
No single component allows you to define the cause of a change.
Thickening
Thickening refers to an increase in the insertion measurement relative to the technical parameters used.
It may be related to edema, inflammation, or chronic overload. However, the thickness varies according to the structure examined, the biotype, the technique, and the population studied.
Hypoechogenicity
Hypoechogenicity occurs when the enthesis appears darker on ultrasound due to an alteration in the reflection of echoes.
It may be part of an inflammatory or tendinopathy pattern. Improper transducer positioning and an artifact called anisotropy can also mimic this alteration.
Loss of fibrillar pattern
The loss of the fibrillar pattern represents less definition of the tendon fibers.
It can occur in tendinopathies, structural changes, or inflammatory processes. It is not a specific finding and should be correlated with other signs.
Calcifications
The calcifications appear as bright spots in the enthesis region, and may or may not produce an acoustic shadow.
They generally represent chronic structural changes or responses to overload. They can also be observed in people without inflammatory disease.
Enthesophytes
Enthesophytes are bony projections that form at the insertion site.
They may represent chronic structural remodeling. Their frequency tends to increase with age and with continuous exposure to mechanical load.
Bone erosions
Erosions are focal discontinuities in the cortical surface of bone, which must be confirmed in different ultrasound planes.
When well characterized, they can reinforce the suspicion of damage associated with an inflammatory disease. Bone irregularities and artifacts, however, can make interpretation difficult.
associated bursitis
Ultrasound can identify distension or changes in bursae near entheses, such as the retrocalcaneal bursa and the deep infrapatellar bursa.
Bursitis can be accompanied by local inflammation, but it can also have a mechanical origin.
Vascularization on Doppler
Doppler ultrasound demonstrates blood flow in the enthesis region.
When properly located, this signal may be related to inflammatory activity. Its detection depends on the equipment settings, temperature, positioning, and pressure exerted by the transducer.
Chronic structural changes
Calcifications, enthesophytes, erosion, and remodeling can represent accumulated damage or structural adaptation.
These changes do not necessarily indicate the presence of active inflammation at the time of the examination.
The OMERACT group's consensus definitions for ultrasonographic enthesitis include hypoechogenicity, increased thickness, erosions, calcifications or enthesophytes, and Doppler signal at insertion.
The OMERACT study also showed that reliability varies between different components and depends on technical standardization.
What is the role of Doppler in the MASEI protocol?
Doppler ultrasound searches for slow-velocity vascularization near the insertion site, a finding potentially related to inflammatory activity.
The significance of the sign depends not only on its presence, but also on its anatomical location.
To detect slow flows, the equipment needs to be sensitively adjusted using appropriate parameters for:
frequency;
gain;
wall filter;
speed scale;
pulse repetition frequency.
Excessive transducer pressure can compress small vessels and obscure the Doppler signal.
The position of the joint, the temperature of the examined region, and movement artifacts can also interfere with the result.
Therefore, the absence of Doppler ultrasound does not rule out enthesitis .
The patient may present with inflammation without detectable vascularization at that time. Current medications and technical limitations can also reduce the sensitivity of the test.
Similarly, a small vascular sign outside the defined topography of the enthesis should not be automatically classified as inflammation.
For which diseases can MASEI ultrasound be helpful?
Ultrasound of the entheses can be particularly helpful in the complementary evaluation of spondyloarthritis.
Clinical contexts include:
Axial spondyloarthritis with peripheral symptoms;
peripheral spondyloarthritis;
psoriatic arthritis;
ankylosing spondylitis;
research on inflammatory enthesitis;
Evolutionary documentation in selected situations.
MASEI alone does not confirm any of these conditions.
Blood tests, X-rays, or MRI scans may be necessary depending on the symptoms, physical examination, and clinical hypothesis.
Who can benefit from MASEI ultrasound?
The examination can be useful when there is clinical suspicion of multiple enthesis involvement or a need for standardized documentation.
This may include people with:
pain in multiple insertions;
Persistent pain in the Achilles tendon;
pain in the heel area;
pain in the soles of the feet;
psoriasis associated with musculoskeletal symptoms;
suspected psoriatic arthritis;
suspected spondyloarthritis;
Symptoms that were not clarified by clinical examination alone;
Specific medical request for enthesitis investigation.
The test may also be requested when the doctor wishes to compare structural changes and potentially inflammatory signs.
The indication should be individualized. Asymptomatic people with psoriasis do not need to undergo MASEI indiscriminately.
MASEI and psoriatic arthritis
Enthesitis is one of the clinical domains of psoriatic arthritis.
However, ultrasound changes in entheses can also appear in people with psoriasis without arthritis and in individuals without inflammatory disease.
In a study that compared patients with psoriatic arthritis, isolated psoriasis, and healthy controls , MASEI scores were, on average, higher among patients with psoriatic arthritis.
Sensitivity, however, was limited at the cutoff point used. The ability to differentiate also decreased among participants with a body mass index above 30 kg/m².
These data reinforce why the score should not be interpreted outside of a clinical context.
In patients with psoriasis, symptoms such as joint pain or swelling, stiffness, dactylitis, and pain at joint insertions should prompt a medical evaluation.
The dermatologist and rheumatologist can determine if an ultrasound for psoriatic arthritis will add relevant information to the investigation.
MASEI and spondyloarthritis
Enthesitis is part of the spectrum of spondyloarthritis, but ultrasound primarily assesses accessible peripheral entheses.
This examination is not a substitute for magnetic resonance imaging (MRI) in the investigation of sacroiliitis or axial inflammation.
In axial spondyloarthritis, symptoms related to the spine and sacroiliac joints predominate, although peripheral manifestations may also be present.
In the peripheral form, enthesitis, arthritis, and dactylitis may play a more significant role.
X-rays, ultrasound, and magnetic resonance imaging are chosen according to the structure that needs to be investigated, the time elapsed since the onset of the disease, and the clinical question.
Does the MASEI score confirm the diagnosis?
No. MASEI should not be used alone to confirm or rule out spondyloarthritis or psoriatic arthritis.
The result needs to be interpreted in conjunction with:
symptoms;
physical examination;
age;
sex;
body mass index;
physical activity;
history of trauma;
metabolic diseases;
presence of psoriasis;
laboratory tests;
other imaging tests.
A high score does not automatically establish a specific disease.
A low or normal result does not rule out the entire spectrum of spondyloarthritis, especially when the manifestation is predominantly axial or when there are technical limitations.
Inflammatory change or mechanical overload?
The distinction between inflammation and overload depends on the pattern and distribution of the findings, not on a single image.
Several factors can modify entheses:
age;
sporting activity;
obesity;
physical work;
repetitive overload;
trauma;
degenerative changes;
Metabolic diseases.
A study conducted with healthy volunteers showed that age, sex, body mass index, and physical activity influence the ultrasound findings of entheses.
Another investigation found findings considered potentially active in some individuals without inflammatory disease, demonstrating that the enthesis of a healthy person can also present variations on ultrasound .
Well-characterized erosions and Doppler ultrasound located in the correct location may increase suspicion of inflammation, but clinical correlation is still required.
Isolated findings of enthesophytes and calcifications, especially in load-bearing areas, may predominantly reflect mechanical or degenerative factors.
How is MASEI ultrasound performed?
The examination is performed using a high-frequency transducer, gel, and different positioning techniques to visualize each enthesis.
The structures are examined in longitudinal and transverse planes.
MASEI ultrasound:
It does not use ionizing radiation;
It generally does not require contrast;
It is performed bilaterally;
It uses grayscale images;
includes Doppler ultrasound assessment;
It allows you to compare both sides;
It is generally non-invasive.
The examiner records the images, takes measurements when appropriate, and activates the Doppler with parameters aimed at identifying slow flow.
The examination is usually well tolerated. Mild discomfort may occur when the transducer is placed on an already painful area.
During Doppler ultrasound, the pressure applied must be minimal to avoid compression of small blood vessels.
Is there any preparation required for the MASEI ultrasound?
In general, MASEI ultrasound does not require fasting or discontinuation of medication.
The patient should not interrupt treatments without guidance from their attending physician.
On the day of the exam, it is recommended to bring:
doctor's order;
previous imaging exams;
Rheumatologist's reports;
Relevant laboratory results;
List of medications currently in use.
It is also important to inform:
diagnosis of psoriasis;
known rheumatological diseases;
sporting activity;
previous surgeries;
history of trauma;
Location and duration of symptoms.
Choose clothing that allows easy access to your elbows, knees, ankles, and feet.
How long does a MASEI ultrasound last?
There is no single validated duration that applies to all patients and services.
The time varies depending on:
patient anatomy;
mobility;
amount of documentation required;
presence of symptoms;
findings found;
The need for additional assessment beyond the traditional score.
When scheduling, Insonify can inform you of the time slot reserved for the protocol performed at the clinic.
How is the result presented?
The report describes the findings from each enthesis and may include a MASEI score when applicable.
The document may include:
bilateral comparison;
measures of the entheses;
structure and echogenicity;
calcifications;
enthesophytes;
bone erosions;
associated bursitis;
presence or absence of vascularization on Doppler ultrasound;
index score;
integrated conclusion.
The conclusion should bring together the components of the examination without transforming the image into a definitive rheumatological diagnosis.
The result should be taken to the referring physician, who will determine its importance within the overall investigation.
What are the limitations of MASEI?
The main limitations of MASEI are the lack of specificity of several findings and the technical dependence on the examination.
Limitations include:
Age, body weight, and physical activity can increase the amount of changes;
Metabolic, degenerative, and mechanical diseases can mimic or coexist with inflammation;
Doppler settings interfere with flow detection;
Transducer pressure can reduce the vascular signal;
The quality of the equipment influences the purchase;
The examiner's experience influences the grading;
There is no single universal value applicable to all populations;
Changes can appear in people without inflammatory disease;
A normal examination does not rule out spondyloarthritis or psoriatic arthritis;
The method is directed at peripheral entheses and does not adequately assess deep axial structures.
Why is the examiner's experience important?
Performing MASEI requires anatomical knowledge, standardization, and mastery of low-velocity Doppler.
Small differences in position, angulation, and pressure can modify the appearance of the enthesis or the vascular signal.
The examiner needs to recognize:
anisotropy;
cortical irregularities;
physiological vessels;
motion artifacts;
mechanical changes;
degenerative changes;
potentially inflammatory signs.
It is also necessary to correctly apply the components of the index and differentiate potentially active signals from accumulated structural damage.
Dr. Patrick Catricala and the realization of MASEI
The MASEI protocol is performed at Insonify by Dr. Patrick Felipe Catricala, CRM-SP 133.006 and RQE 46.844, specialist in Radiology and Diagnostic Imaging.
Their work focuses on:
musculoskeletal ultrasound;
Doppler applied to rheumatology;
Ultrasound evaluation of entheses;
MASEI protocol;
Ultrasound-guided procedures.
Dr. Patrick also works in teaching activities in the musculoskeletal sector at the Federal University of São Paulo.
The institutional page for the musculoskeletal sector at Unifesp identifies him as a "Facilitator/Professor" for the "Image in the Spine" activity.
Experience in musculoskeletal anatomy, ultrasonography, and medical education contributes to standardized execution and careful interpretation of the examination.
Also check out Dr. Patrick Catricala's professional page on Insonify .
MASEI Ultrasound in Moema, São Paulo
Insonify performs MASEI ultrasound in Moema, São Paulo, with bilateral enthesis assessment and rheumatological Doppler.
The clinic is located at:
Insonify Ultrasound, Avenida Jamaris, 616, Moema — São Paulo/SP, CEP 04078-001
Patients and referring physicians seeking MASEI in São Paulo, enthesis ultrasound in São Paulo, rheumatological Doppler in Moema, or musculoskeletal ultrasound in Moema can contact the clinic to confirm availability, instructions, and required documentation.
Frequently asked questions about MASEI ultrasound
What does MASEI mean?
MASEI stands for Madrid Sonographic Enthesis Index.
What are entheses?
Entheses are regions where tendons, ligaments, joint capsules, or fascia insert into bone.
What is enthesitis?
Enthesitis is inflammation of the enthesis. It can cause pain and stiffness, but not all pain in this region has an inflammatory origin.
What is the MASEI ultrasound used for?
The examination serves to document, in a standardized manner, structural changes and potentially inflammatory signs in peripheral entheses.
Which entheses are evaluated?
The protocol bilaterally assesses the insertions of the triceps, quadriceps, proximal and distal patellar tendons, Achilles tendon, and plantar fascia.
Does MASEI diagnose spondyloarthritis?
No. The MASEI is a complementary test and does not confirm or rule out spondyloarthritis on its own.
Does this test help in the investigation of psoriatic arthritis?
It can be helpful when clinically indicated, especially in people with psoriasis associated with musculoskeletal symptoms.
What is the function of Doppler ultrasound?
Doppler ultrasound scans for slow-velocity vascularization in the enthesis region, which may be related to inflammatory activity.
Does the absence of Doppler ultrasound rule out inflammation?
No. The absence of Doppler does not rule out enthesitis, as detection depends on the stage of the disease, medications, technique, and equipment.
Does the test evaluate the Achilles tendon?
Yes. The insertion of the Achilles tendon into the calcaneus is examined bilaterally.
Does MASS EI assess the plantar fascia?
Yes. The origin of the plantar fascia near the calcaneus is part of the traditional protocol.
Does the exam hurt?
Generally not. There may be slight discomfort when the transducer touches an area that is already painful.
Does the examination use radiation?
No. Ultrasound uses sound waves and does not employ ionizing radiation.
Is fasting necessary?
Generally, no. You should also not stop taking medication without medical advice.
Could the MASEI be altered in athletes?
Yes. Physical activity and mechanical load can influence the thickness, structure, and other findings of entheses.
Can being overweight influence the outcome?
Yes. Body mass index can increase changes related to mechanical load and decrease the ability to differentiate in some contexts.
A normal MASS EI excludes rheumatological disease?
No. A normal result does not rule out spondyloarthritis, psoriatic arthritis, or predominantly axial disease.
Which doctor usually orders the test?
The rheumatologist is the primary requester. Orthopedists, physiatrists, sports medicine doctors, and dermatologists may also request it, depending on the case.
Where can I take the MASEI course in São Paulo?
Insonify offers the MASEI protocol in Moema, São Paulo, by appointment.
Who performs the exam at Insonify?
The examination is performed by Dr. Patrick Felipe Catricala, specialist in Radiology and Diagnostic Imaging, CRM-SP 133.006 and RQE 46.844.
Conclusion
MASEI is a standardized and complementary ultrasound assessment of entheses.
The protocol allows for the documentation of structural changes and the detection of signs of inflammatory activity using Doppler ultrasound.
However, their findings need to be correlated with symptoms, physical examination, history, laboratory tests, and other imaging methods.
MASEI should not be used alone to confirm or rule out spondyloarthritis, psoriatic arthritis, or other rheumatological diseases.
For information on performing Doppler ultrasound using the MASEI protocol, please contact us.
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