Soft Tissue Masses of the Knee Related to a Focal Defect of the Lateral Patellar Retinaculum.

  • Moraux Antoine
  • Bianchi Stefano
  • Le Corroller Thomas

  • Humans
  • Aged
  • Female
  • Male
  • Middle Aged
  • 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

ART

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.