About this trial

The ETICHOFFA study is a clinical research project aiming to improve the diagnosis of Infrapatellar fat pad impingement syndrome, a common source of anterior knee pain. Although MRI remains the gold standard for diagnosis, clinical testing strategies lack validation. This observational study has two main objectives: to assess the diagnostic accuracy of a cluster of standardized clinical provocation tests for IFP impingement compared to MRI findings, and to identify clinical and subjective characteristics associated with IFP involvement confirmed by imaging.

This observational study will recruit 50 patients aged 18 to 70 years with anterior knee pain rated at least 3 out of 10 in intensity. Participants will complete a secure online questionnaire documenting symptoms, pain distribution, aggravating and relieving factors, and pain intensity at rest, during activity, and daily life. They will also complete three validated scales: the Anterior Knee Pain Scale (AKPS), the Knee injury and Osteoarthritis Outcome Score (KOOS), and the Tampa Scale for Kinesiophobia (TSK).

A standardized clinical examination will be performed, including subpatellar skin temperature measurement, knee swelling assessment, passive range of motion testing, and a series of provocation tests targeting Hoffa's fat pad. Tests will be randomized to reduce bias and considered positive if they reproduce the patient's typical pain with an intensity of at least 2/10. Each participant must also undergo a standardized MRI of the knee within two weeks of the clinical assessment, interpreted blindly by an independent musculoskeletal radiologist.

All data will be anonymized, stored securely, and analyzed using SPSS software. Diagnostic accuracy of clinical tests will be evaluated through sensitivity, specificity, predictive values, and likelihood ratios. Functional outcomes related to taping will also be analyzed.

The study has received ethical approval and adheres to GDPR standards for data protection. Participation is voluntary, with the right to withdraw at any time. The ETICHOFFA study is expected to enhance clinical diagnostic pathways for anterior knee pain associated with Infrapatellar fat pad involvement.

Eligibility criteria

This trial does not accept healthy volunteers

Qualifiers

Age between 18 and 70 years

Presence of anterior knee pain with an intensity of ≥3/10 on the Numerical Rating Scale (NRS), on most days over the past month

MRI of the knee performed within a maximum of 15 days before or after the clinical examination.

Disqualifiers

History of corticosteroid injection treatment within the previous 12 months;

Known allergy or skin intolerance to medical adhesives or rigid tape;

History of hip or lumbar spine surgery;

History of neurological disorders or a diagnosis of fibromyalgia;

Trial population

Adults aged 18 to 70 years experiencing anterior knee pain (AKP) rated ≥3/10 for at least 4 weeks will be eligible. Patients will be recruited from the department of orthopedic and trauma at Hôpital Paris-Est Val de Marne (Saint-Maurice), including both postoperative cases (e.g., post-arthroscopy) and non-surgical patients referred for expert consultation regarding persistent or unexplained anterior knee pain.

Trial design

Design model

Cohort

Time perspective

Cross-sectional

Treatments tested in this trial

Provocative test
Diagnostic test
The clinical evaluation specific to Infrapatellar fat pad is based on a series of five standardized clinical tests, extensively described in the specialized literature: provoked palpation of the fat pad, provoked passive extension, Hoffa's test, gliding test, and provoked passive flexion. These tests are performed in a randomized order to limit sequence bias. A test is considered positive if it reproduces the patient's typical anterior knee pain with an intensity greater than 2/10 on the numerical pain scale. Although widely used, these tests have not yet undergone rigorous methodological validation, which this study specifically aims to address.

Treatment groups

No treatment groups listed

Trial outcomes

Primary outcomes

1

The primary endpoint of this study is the diagnostic value of the five clinical tests targeting the infrapatellar fat pad, considered collectively as a test cluster.

The overall performance of the test cluster will be analyzed using contingency matrices comparing the combined clinical test results with MRI findings. Various combination strategies will be tested (e.g., ≥2 positive tests out of 5), and the following diagnostic validity indices will be calculated for each threshold: sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive and negative likelihood ratios (LR⁺, LR-). ROC curves will be generated, and the area under the curve (AUC) will be used as a synthetic indicator of the cluster's discriminative capacity, with an AUC ≥ 0.80 considered clinically meaningful.

Time frame

At baseline (post-imaging and clinical assessment)

Secondary outcomes

1

Diagnostic performance of individual clinical tests

A set of five standardized clinical tests targeting Hoffa's fat pad will be performed on the symptomatic knee and analyzed individually against MRI findings. Four tests are pain provocation tests, and one is a mobility assessment. Diagnostic accuracy will be evaluated using sensitivity, specificity, predictive values (PPV, NPV), and likelihood ratios (LR⁺, LR-), with 95% confidence intervals. For the mobility test, ordinal logistic regression and diagnostic performance across categories will be explored. All tests will be conducted during the initial clinical examination. The diagnostic value of each test will be compared independently to MRI-confirmed Infrapatellar pad impingement. Unit of Measure: diagnostic accuracy metrics (Se, Sp, PPV, NPV, LR⁺, LR-); ordinal score (gliding test)

Time frame

At baseline (post clinical assessment)

2

Post-test probability of Infrapatellar fat pad impingement (Fagan nomogram analysis)

To estimate the clinical decision-making utility of each provocation test, the post-test probability of Hoffa's fat pad impingement will be calculated based on positive and negative likelihood ratios (LR⁺ and LR-) derived from diagnostic performance data. A pre-test probability will be defined using the observed prevalence in the study cohort. Post-test probabilities will be determined using Bayesian reasoning and represented graphically using Fagan nomograms. This analysis aims to illustrate how individual test results impact diagnostic certainty and assist in clinical reasoning.Unit of Measure: Post-test probability (%)

Time frame

At baseline (post-imaging and clinical assessment)

3

Infrapatellar skin temperature at rest (lying position)

A localized skin temperature measurement will be performed using a non-contact infrared laser thermometer, approximately 1 cm below the inferior pole of the patella (infrapatellar region). This will be the first measurement taken on the knee, about 10 minutes after the start of the consultation, with the patient in a seated position at rest. It will be performed before any physical contact with the knee, to avoid influencing local temperature.Unit of Measure: degrees celsius (°C)

Time frame

At baseline (during initial clinical assessment)

4

Presence of intra-articular swelling (Stroke Test)

The presence of intra-articular effusion will be assessed using the standardized Stroke Test (also known as the bulge test). The patient will be in a supine position with the knee in full extension. The examiner will use a sweeping motion to displace fluid medially and laterally around the patella. The result will be graded on a 4-point scale (0 = no wave, 1 = small wave on medial side, 2 = larger bulge, 3 = spontaneous return without sweeping). This test will be performed early in the clinical examination, before any active or passive knee mobilization.Unit of Measure: Grading scale (0 to 3)

Time frame

At baseline (during initial clinical assessment)

Diagnostic Validity Ofclinical Tests for Infrapatellar Fat Pad Impingement Syndrome

About this trial

Eligibility criteria

Qualifiers

Disqualifiers

Trial population

Trial design

Treatments tested in this trial

Treatment groups

Trial outcomes

Primary outcomes

Secondary outcomes

Other outcomes

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