Fabella and patella variants: radiographic prevalence, distribution and clinical relevance in a population of black African descent

To evaluate the radiographic characteristics and prevalence of fabella and patella variants in an indigenous African population. This retrospective observational study of orthogonal knee radiographs of 377 consecutive subjects was conducted in Lagos, Nigeria, from February 2017 to November 2017. The presence of bipartite/multipartite patella, as well as the presence of fabella were noted. The craniocaudal diameter, anteroposterior diameter, fabello-femoral distance and fabello-tibial distance of the fabella were measured. P≤0.05 represented a statistically significant result. Three hundred and seventy-seven subjects were enrolled. The average age was 41.22±21.37 years with a range of 3–100 years old. There were 158 male (41.9%) and 219 female (58.1%) subjects. The prevalence of fabella was 11.94%. There was a positive correlation between age <47 and ≥47 and occurrence of fabella, P<0.015. There was no statistically significant difference between the mean male and female measured fabella diameters. The overall prevalence of bipartite and multipartite patella in this study was 2.12%. Among male and female subjects, the difference in prevalence of bi and multipartite patella was statistically significantly, P=0.03. The prevalence of fabella and patella variants was lower in this study compared to the findings in other populations and ethnicities. Sex and age were significantly correlated with fabella prevalence. The results reported in this study will facilitate future studies examining the correlations between fabella and patella variants and various knee pathologies in a population of Black African descent.