Anatomical study of the fabella, fabellar complex and its clinical implications.

The fabella has been mainly studied using imaging methods but there are less research reports on the gross anatomical studies. We performed this anatomical study of the fabella and its surrounding structures with functional implications using 150 heads of the gastrocnemius muscles of 75 knees from 39 Japanese cadavers. This study is the direct representation of the human fabella and its functional implications. We observed 99 fabellae (66.0%) including 44 complete bony fabellae (29.3%). Of these bony fabellae, 43 (97.7%) were located in the lateral head of the gastrocnemius muscle with its surrounding structures and were positioned only on the lateral condyle of the femur. Moreover, the cartilage and bony fabellae, especially on the lateral side, contributed to the fabella complex with its surrounding muscles and ligaments and formed small articular cavity by cooperating with the femoral condyle. Although the human fabella is considered as appearing in the fabella complex with ageing and it possibly induces clinical symptoms, the fabella may play an important role as a stabilizer between the fabella complex and the femoral condyle.