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

Abstract

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.

Incidence and radiological characteristics of fabellae in an Asian population

“…Similar to previous studies, (4,6,9) we did not find any statistically significant difference in the incidence of fabellae between men and women. However, in our cohort, the fabellae were consistently larger in men than in women.…”

“…(6,9) This difference could be attributed to the inherent cultural differences between the populations studied. For instance, tatami mats are a deeply rooted tradition in Japanese culture, and the Japanese people have a predilection for kneeling on these mats during social functions.…”

“…(2,3) In humans, however, the fabella is not always present, with the reported incidence ranging between 8.7% and 31.3% in western populations, (4,5) and between 66.0% and 85.8% in Japanese populations. (6,7) Various cadaveric studies on the fabella have described its anatomy, relationship with the surrounding tissues, and clinical implications. (5) Imaging studies, mainly case reports, have described the fabella in relation to clinical scenarios such as osteoarthritis (6) and pain following total knee arthroplasty.…”

“…(6,7) Various cadaveric studies on the fabella have described its anatomy, relationship with the surrounding tissues, and clinical implications. (5) Imaging studies, mainly case reports, have described the fabella in relation to clinical scenarios such as osteoarthritis (6) and pain following total knee arthroplasty. (8) However, those imaging studies did not adequately describe the radiological characteristics of the fabella.…”

A new insight into the fabella at knee: the foetal development and evolution

“…The incidence and bony nature of fabellae in human adults has been found to vary, with studies showing incidence rates of 66.6% (44% bony) [8]; 23.5% (72% bony) [13]; 86.9% (56% bony) [24]; and 31% (100% bony) [3]. Almost half of fabellae carry a facet for articulation to the lateral femoral condyle [3].…”