Table 3 Prevalence rates broken down by subcategories (individuals, knees) and sex.
| Knees | Individuals | Percentage bilateral | Percentage unilateral | |
| Male | 41.18% (42/102) | 47.06% (24/51) | 75.00% (18/24) | 25.00% (6/24) |
| Female | 47.27% (52/110) | 58.18% (32/55) | 62.50% (20/32) | 37.50% (12/32) |
| Total | 44.34% (94/212) | 52.83% (56/106) | 67.86% (38/56) | 32.14% (18/56) |
There were no sex-based differences. Of the 56 individual cases, bilateral cases were significantly more prevalent than unilateral ones. Bilateral cases were more prevalent than unilateral in males (n = 24), but there was no difference in females (n = 32). Within unilateral cases, fabellae were equally likely to be present in the right or left knee. There were no differences between the sexes (see text for test statistics and P-values).
Table 4 Results showing no correlation between height/age and prevalence of fabellae in individuals, or the percentage of bilateral/unilateral cases (i.e. are taller individuals more or less likely to have bilateral fabellae?). Degrees of freedom were all 104, P-values were all > 0.25. (r = correlation coefficient; t = test statistic). Individuals
| Individuals | Percentage bilateral | Percentage unilateral | ||||
| r | t | r | t | r | t | |
| Height | -0.0245 | -0.2502 | 0.0574 | 5867 | -0.106 | -1.0869 |
| Age | 0.0601 | 0.6143 | -0.0136 | -0.1384 | 0.0973 | 0.9967 |
Chinese). It should be noted that the authors are not confident they identified all non-English studies, as it is possible non-English studies exist without translated titles/abstracts and as such were not detected by our search terms. Also, we are not confident we identified all studies < 75 years old, as we discovered some in bibliographies that did not come up in our scholar.google.co.uk searches. A total of 185 full-text articles/conference proceedings were reviewed, 66 of which reported on fabella prevalence rates. Of the 66 studies, five were discarded from further analysis as they did not fit the inclusion criteria. Pancoast (1909) and Hukuda et al. (1983) reported that 67/529 and 11/31 individuals from the USA and Japan, respectively, had fabellae, but these could not be transformed into a knee prevalence rate (Pancoast, 1909; Hukuda et al. 1983). Chew et al. (2014) reported on a prevalence rate of 31.25% (25/ 80) in 'Asians', but we could not determine whether this was an individual or knee rate (Chew et al. 2014). Siina (1931), taken from Table 1 (tabelle I) in Hessen (1946), and Munshi et al. (2003), had a sample sizes of 10 and 8 knees, respectively (Munshi et al. 2003). Finally, three studies claimed to have data on fabella presence/absence, but the data were not present, at least not in the versions of the papers we had access to (Nishimura & Shimizu, 1963; Orzincolo et al. 1987; Osti et al. 2013). Our final analysis included 21 676 knees and represented studies done in 27 countries. It should be noted that Taiwan was part of Japan from 1895 to 1945, at the time of studies of Kitahara (1935) and Hanamuro (1927). According to Hessen (1946), Kitahara's (1935) sample was 'Formosawilde', indicating it consisted of
Fig. 2 Lateral (left) and superior (right) views of the fabella (white arrow).
