Soft Tissue Masses of the Knee Related to a Focal Defect of the Lateral Patellar Retinaculum.
Résumé
We report on the imaging features of 6 soft tissue masses in the anterolateral aspect of the knee related to a focal defect of the lateral patellar retinaculum. In 4 patients (3 female and 1 male; 6-65 years) presenting with nontender palpable soft tissue masses in the anterolateral aspect of their knees, ultrasonography showed a focal defect of the lateral patellar retinaculum with herniation of the Hoffa fat pad, which was only visible in flexion. A magnetic resonance imaging examination performed in 1 case confirmed the defect in the lateral patellar retinaculum but did not show a mass, as the knee was examined only at 10° of flexion. The 2 remaining patients (one male and 1 female; 62 and 55 years) presented with soft tissue masses in their anterolateral knees in both flexion and extension. These masses were related respectively to a lipoma of the Hoffa fat pad and to a ganglion cyst, both herniated through a defect of the lateral patellar retinaculum. Our cases suggest that a focal defect of the lateral patellar retinaculum may be a route for Hoffa fat pad herniation as well as a route for superficial extension of infrapatellar fat lesions such as lipomas and ganglion cysts.
Mots clés
Ultrasonography/*methods
Child
Diagnosis
Differential
Knee Joint/*diagnostic imaging
Adipose Tissue/diagnostic imaging
ganglion cyst
Ganglion Cysts/diagnostic imaging
Hoffa herniation
Joint Diseases/*diagnostic imaging
lateral patellar retinaculum defect
lipoma
Lipoma/*diagnostic imaging
Magnetic Resonance Imaging/methods
musculoskeletal (diagnostic)
Patellar Ligament/*diagnostic imaging
pediatrics
soft tissue masses
Soft Tissue Neoplasms/*diagnostic imaging
Humans
Aged
Female
Male
Middle Aged