Table 1 Average and median age and heights for our sample, divided by sex. Men are taller than women.
| Age (years) | Height (cm) | ||||
| Mean ± SD | Median (Q1, Q3) | Mean ± SD | Median (Q1, Q3) | ||
| Male | 50.86 ± 9.82 | 54 (44, 59) | 165.41 ± 6.33 | 164 (161, 170) | |
| Female | 53.93 ± 8.07 | 57 (51, 60) | 156.24 ± 5.08 | 156 (153, 160) | |
| Total | 52.45 ± 9.05 | 55 (47, 60) | 160.65 ± 7.32 | 160.5 (155, 165) | |
Systematic review
Data sources
To complete a comprehensive literature review, the following search strategies were used for the systematic review: (1) computer search of databases and (2) review of bibliographies of all articles retrieved. Textbooks were not utilized unless they specifically came up in the computer search or bibliographies. This strategy is in accordance with Stroup et al. (2000).
Computer search
We searched google.scholar.co.uk for articles pertaining to the fabella in April 2018 and updated our results in October 2018. The search term fabella yielded 9140 results, many of which were not relevant to this study. To narrow the results, the following search terms were employed: fabella sesamoid, fabellae sesamoid -fabella, fabella knee -sesamoid, fabellae knee –sesamoid -fabella, cyamella –fabella -fabellae, fabella incidence rate –sesamoid -knee, fabellae incidence rate –sesamoid –knee -fabella, fabella prevalence rate –sesamoid –knee -incidence, and fabellae prevalence rate -sesamoid knee -fabella -incidence. A hyphen before a word indicates the following word was excluded from that search, preventing the same article/citation from appearing in multiple searches.
Abstracts were reviewed first by M.A.B., and later by E.D.F. if necessary, and selected for further review if they met the following criteria: (1) the studies were on humans, (2) the studies were anatomical or medical in nature, (3) not case studies, and (4) a link was provided through which the article could be accessed. Full texts were reviewed by M.A.B.. Studies were excluded if they (1) did not report on prevalence or incidence rates based on data gathered in that study, (2) calculated rates with samples <12 knees, (3) did not report on the number of knees analysed in the study or (4) did not use a randomized sample (e.g. studies on fabella syndrome). If studies were not written in English, they were translated either by people fluent in those languages or using google translate. While imperfect, google translate worked well enough to extract the necessary data.
Review of bibliographies
If papers referenced other studies on prevalence rates, full texts of those studies were obtained through scholar.google.co.uk or interlibrary loan. If the original studies could not be located (as was the case with several older studies), data were extracted from the paper that referenced the original study, when possible. If not possible, the original study was excluded.
Statistical analysis
Korean dataset
R and Rstudio were used for statistical analyses (R Team, 2015; R Core Team, 2018). Prevalence rates for the Korean population were calculated as the percentage of knees with fabellae and individuals with fabellae. For those with fabellae, the percentage of bilateral and unilateral cases was calculated. Pearson's chi-square tests were performed using the chisq.test function (simulate P-value = TRUE, B = 10 000) to investigate the correlation between sex and prevalence rates. The simulate-P-value simulates datasets using Monte Carlo simulations to estimate P-values for chi-square tests. A Pearson's chi-square test was performed with the unilateral data to investigate bilateral asymmetry. Point biserial correlations with
Fig. 1 Large (left), medium (centre), and small (right) ossified fabellas in the right knees of three female subjects.
