Edema superoexterno de grasa de Hoffa: signo de rótula alta y su asociación clínica

Abstract

Introduction: the importance of the peripatellar fat pads in the normal kinematics of the knee is a fundamental factor. Patella alta is one of the most important etiologic factors of patellofemoral instability and is considered a predisposing factor for the development of patellofemoral pain. The objective of this work was to demonstrate the magnetic resonance findings of the involvement of the external superolateral sector of Hoffa's fat due to edema, as a sign suggestive of a long patellar tendon with patella alta, and to evaluate its symptoms.

Materials and methods: a series of patients and their MRIs of the knee performed in our center between 2019 and 2022 were retrospectively evaluated. Edema was found in the upper external region of Hoffa's fat in the sagittal, coronal, and axial planes. , patellar height measurements were made using the Insall-Salvati method on MRI in a sagittal cut in T2 sequence. The reason for consultation and the relationship with the observed image were evaluated.

Results: a total of 119 MRIs were evaluated, corresponding to 104 patients. In fifteen patients both knees were evaluated. They were sixty-five females and thirty-nine males. The average age was 32.8 years (14-75 years). Upper outer edema of Hoffa's fat was evidenced in all the evaluated MRIs, observing the long patellar tendon in 117 knees, which represented 98.3% of the sample. The average patellar height was 1.49 according to the IS index (1.12-2.03). Two MRIs (1.7%) showed edema with patellar height with normal values of 1.12 and 1.18.

Discussion: upper external edema of Hoffa's fat has a strong relationship with elevated patellar height. These variables were studied in this work and an attempt was made to establish a relationship between them. The patella alta evaluation method, the Insall-Salvati index, is the most reliable. Several studies correlate upper outer edema and patella alta, some of them associated with young patients, while others associate it with signs of osteoarthritis and older patients. As for the symptoms that cause these findings, they are unclear.

Conclusion: in the present study, it was evidenced that there is a strong relationship between the upper external edema of Hoffa's fat and a patella alta, making this a very useful sign when studying and understanding patellofemoral pathology. We observed a greater association with patellofemoral symptoms and knee trauma, despite this being seen in other pathologies.