Jhonatan Duque-Colorado; Carlos Alberto Duque-Parra; Mariano del Sol

The fabella is a bony anatomical variable, which in humans is located posterior to the lateral condyle of the femur, in the tendinous portion of the lateral head of the gastrocnemius muscle. Its prevalence rate has been reported in different populations, ranging from 3% to 86%. This study aimed to create an index that classifies the fabella according to its dimensions, determine the prevalence of the fabella in the Colombian population, and identify possible differences according to the fabella index (FI), sex, age, laterality, and degree of fabellar degeneration. A retrospective study used 93 lateral knee radiographs belonging to Colombian individuals. A fabella index was established to classify fabellae into longifabellar, medifabellar, and equifabellar, and radiological classification was used to identify the degree of fabellar degeneration (DFD). The prevalence of fabella was 36.30 %, and this variant was associated with the individual’s sex, with male subjects having 2.66 times the probability of presenting fabella. A higher prevalence of medifabellar fabellae (57.60 %) was observed, followed by longifabellar (24.20 %) and equifabellar (18.20 %). There was a positive and moderate correlation between the DFD and age. We consider that larger fabellae can cause entrapment of the common fibular nerve, compression of the popliteal artery, and tear of the medial meniscus, so the FI becomes relevant in clinical practice, providing information on the type of fabella and its associated pathological manifestations. This study introduces a novel fabella index and investigates the frequency of fabella in the Colombian population. The findings of this study will serve as a reference for future research and contribute to the field of knee orthopedics and surgery in this population.

KEYWORDS: Anatomy; Fabella; Fabella index; Prevalence; Radiology.

DUQUE-COLORADO, J.; DUQUE-PARRA, C. A. & DEL SOL, M. Prevalence of the fabella and determination of the fabella index. Int. J. Morphol., 42(3):814-818, 2024.