The macroscopic arthroscopic anatomy of the infrapatellar fat pad.

Purpose: Our purpose was to define the macroscopic anatomy of the infrapatellar fat pad (IFP) when viewed at arthroscopy and to document the common variations.

Methods: Ninety-six consecutive patients between 8 and 50 years of age with no previous knee surgery or fat pad pathology underwent arthroscopic examination of the knee. The fat pad of each patient was observed and described regarding size, color, consistency, and the presence of lobules, villous synovium, and lingulae.

Results: The macroscopic arthroscopic anatomy of the IFP was defined. Male fat pads were larger than female fat pads. Two separate parts were described-medial and lateral-with medial dominence being most typical. The specific normal anatomic appearance of each section was defined regarding size, color, consistency, and attributes. Ligamentum mucosum, as the separation limit between the sections, was found in most knees.

Conclusions: The macroscopic anatomy of the IFP is described at arthroscopy performed for internal pathology of the knee. Two distinct parts were defined-medial and lateral-with medial dominance. A typical fat pad was yellow and included an infrapatellar lingula (85%), lobulation (65%), and villous synovium (65%). We found a ligamentum mucosum in 79% of cases.

Clinical Relevance: Knowledge of the macroscopic anatomy of the IFP and variations will allow the accurate diagnosis of pathology of the fat pad, rather than being a diagnosis of exclusion.