Functional and Structural Details about the Fabella: What the Important Stabilizer Looks Like in the Central European Population

The fabella is a sesamoid bone located behind the lateral femoral condyle. It is common in non‐human mammals, but the prevalence rates in humans vary from 3 to 87%. Here, we calculate the prevalence of the fabella in a Korean population and investigate possible temporal shifts in prevalence rate. A total of 52.83% of our individuals and 44.34% of our knees had fabellae detectable by computed tomography scanning. Men and women were equally likely to have a fabella, and bilateral cases (67.86%) were more common than unilateral ones (32.14%). Fabella presence was not correlated with height or age, although our sample did not include skeletally immature individuals. Our systematic review yielded 58 studies on fabella prevalence rate from 1875–2018 which met our inclusion criteria, one of which was an outlier. Intriguingly, a Bayesian mixed effects generalized linear model revealed a temporal shift in prevalence rates, with the median prevalence rate in 2000 (31.00%) being ~ 3.5 times higher than that in 1900 (7.64%). In all four countries with studies before and after 1960, higher rates were always found after 1960. Using data from two other systematic reviews, we found no increase in prevalence rates of 10 other sesamoid bones in the human body, indicating that the increase in fabella prevalence rate is unique. Fabella presence/absence is due to a combination of genetic and environmental factors: as the prevalence rates of other sesamoid bones have not changed in the last 100 years, we postulate the increase in fabella prevalence rate is due to an environmental factor. Namely, the global increase in human height and weight (due to improved nutrition) may have increased human tibial length and muscle mass. Increases in tibial length could lead to a larger moment arm acting on the knee and on the tendons crossing it. Coupled with the increased force from a larger gastrocnemius, this could produce the mechanical stimuli necessary to initiate fabella formation and/or ossification.

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“…; Hauser et al. ). Although its exact function is unknown, the fabella is more common in non‐human mammals (Pearson & Davin, ; Sarin et al.…”

Section: Introductionmentioning

confidence: 98%

“…), X‐rays (Pancoast, ), computed tomography (CT) scans (Hauser et al. ), and magnetic resonance imaging (MRI) scans (Hedderwick et al. ).…”

Section: Introductionmentioning

confidence: 99%

Fabella prevalence rate increases over 150 years, and rates of other sesamoid bones remain constant: a systematic review

2019

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“…The fabella lacks articular cartilage and is, in addition, connected by the fabellofibular ligament to the fibular tip and to the proximolateral side of the meniscus by two separate bundles of fibers (Jin et al, 2017). These anatomical differences imply that, unlike patella, the function of the fabella is not to facilitate and enhance movement but rather restrict it by anchoring and stabilizing the knee, thus preventing possible external rotation of the tibia or hyperextension of the knee (Hauser et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Common cellular origin and diverging developmental programs for different sesamoid bones

et al. 2019

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Sesamoid bones are small auxiliary bones that form near joints and contribute to their stability and function. Thus far, providing a comprehensive developmental model or classification system for this highly diverse group of bones has been challenging. Here, we compare our previously reported mechanisms of patella development in the mouse with those of two anatomically different sesamoids, namely lateral fabella and digit sesamoids. We show that all three types of sesamoid bones originate from Sox9 + /Scx + progenitors under the regulation of TGFβ and independently of mechanical stimuli from muscles. Whereas BMP2 regulates the growth of all examined sesamoids, the differentiation of lateral fabella or digit sesamoids is regulated redundantly by BMP4 and BMP2. Next, we show that whereas patella and digit sesamoids initially form in juxtaposition to long bones, lateral fabella forms independently and at a distance. Finally, our evidence suggests that, unlike the synovial joint that separates patella from femur, digit sesamoids detach from the phalanx by formation of a fibrocartilaginous joint. These findings highlight both common and divergent molecular and mechanical features of sesamoid bone development, which underscores their evolutionary plasticity.

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“…However, the enormous amount of research published about them over more than a century tells another story. Sesamoids have been intensively studied in the context of clinical research, producing an extensive literature (Gruber, ; Pfitzner, ; Müller, ; Pires de Lima, ; Skillern, ; Bizarro, ; Gunn, ; Kewenter, ; Sindberg, ; Stener, ; Scapinelli, , , ; Ellis et al, ; Helal, ; Weiner & Macnab, ; Wood, ; Hansen & Peterson, ; Goldberg & Nathan, ; Le Minor, , , , ; McBryde Jr & Anderson, ; Gibeault et al, ; Bianchi et al, ; Lennox et al, ; Bareither, Muehleman & Feldman, ; Richardson, ; Duncan & Dahm, ; Mellado et al, ; Feller et al, ; Griffith et al, ; Bakerly & Saleh, ; Seki, Hoshino & Kuroda, ; Chen et al, ; Hauser et al, ; DeCamp & Schaefer, ; Tzatzairis et al, ; Vaz & Trippia, ; Yammine, ; Dalip, Iwanaga & Oskouian, ; Berthaume, Di Federico & Bull, , among many others). This represents an enormous and continued interest over time.…”

Section: Introductionmentioning

confidence: 99%

Sesamoids in tetrapods: the origin of new skeletal morphologies

et al. 2019

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Along with supernumerary bones, sesamoids, defined as any organized intratendinous/intraligamentous structure, including those composed of fibrocartilage, adjacent to an articulation or joint, have been frequently considered as enigmatic structures associated with the joints of the skeletal system of vertebrates. This review allows us to propose a dynamic model to account for part of skeletal phenotypic diversity: during evolution, sesamoids can become displaced, attaching to and detaching from the long bone epiphyses and diaphysis. Epiphyses, apophyses and detached sesamoids are able to transform into each other, contributing to the phenotypic variability of the tetrapod skeleton. This dynamic model is a new paradigm to delineate the contribution of sesamoids to skeletal diversity. Herein, we first present a historical approach to the study of sesamoids, discussing the genetic versus epigenetic theories of their genesis and growth. Second, we construct a dynamic model. Third, we present a summary of literature on sesamoids of the main groups of tetrapods, including veterinary and human clinical contributions, which are the best-studied aspects of sesamoids in recent decades. Finally, we discuss the identity of certain structures that have been labelled as sesamoids despite insufficient formal testing of homology. We also propose a new definition to help the identification of sesamoids in general. This review is particularly timely, given the recent increasing interest and research activity into the developmental biology and mechanics of sesamoids. With this updated and integrative discussion, we hope to pave the way to improve the understanding of sesamoid biology and evolution.

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Functional and Structural Details about the Fabella: What the Important Stabilizer Looks Like in the Central European Population

Cited by 32 publications

References 35 publications

Fabella prevalence rate increases over 150 years, and rates of other sesamoid bones remain constant: a systematic review

Fabella prevalence rate increases over 150 years, and rates of other sesamoid bones remain constant: a systematic review

Common cellular origin and diverging developmental programs for different sesamoid bones

Sesamoids in tetrapods: the origin of new skeletal morphologies

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