On the superolateral side, the concave defect is accentuated, with pronounced osteophytosis on the posterior end.
Discussion and Conclusion
In this study, two physically similar but etiologically distinct conditions were recognized. Six patellae from Malo Libinje display superolateral concave defects, a relatively rare finding in archaeological populations (Messina & Sineo, 2007). These defects were diagnosed as bipartite patella and vastus notch.
Patella D has a porous, roughed-edged lesion known as bipartite patella. It is a condition where patella is composed of two separate bones. Based on the location of the secondary ossification center, it is possible to diagnose Patella D as bipartite patella type III (Saupe, 1921). Secondary ossification centers of the patella appear around twelve years of age (Ogden, 1984), and if they later fail to merge, a bipartite patella develops. Separate ossicle may stay detached or can fuse incompletely (Green, 1975). In Patella D’s case from Malo Libinje, the ossicle is detached and is not present, as it often occurs in skeletal assemblages. Some authors suggest mechanical stress (Oetteking, 1922) or repeated microtrauma (Todd & McCally, 1921; Green, 1975) as possible causes. Usually, bipartite patella is considered asymptomatic (Atesok et al., 2008). In some cases, it is a source of persistent pain and can even cause complete disability in the knee (Messina & Sineo, 2007). In treatment of painful patella, the most common surgical approach is excision of distressing fragment (Weckström et al., 2008).
The oldest known example of bipartite patella dates back to 49,000 years ago to the Neandertals from El Sidrón cave (Spain) where a small, probably left tripartite patella with separate ossification center located inferiorly was recovered (Rios et al., 2019). Since bipartite patella with separate ossification center located superolaterally is the most common morphological variant, such a condition is even rarer. Another example of bipartite patella from archaeological context was recorded at the Palaeochristian necropolis of San Giovanni in Marsala, Sicily (Messina & Sineo, 2007). This left patella shows lack of ossification on the lateral side, which can be diagnosed as bipartite patella type II (Saupe, 1921). Furthermore, a bipartite patella was discovered in a skeleton of a 13-15 years old juvenile from the cemetery associated with Franciscan friary at St. Faith’s Lane in Norwich, England dated between the 13th and 16th century CE (Anderson, 2002). In this case the fracture line is clearly visible on the right patella and the resultant ossicle is fused incompletely (Anderson, 2002). The bipartition of the patellae of two skeletons from Pilanesberg National Park, South Africa dated to the Late Iron Age (ca 1300 to 1820/1830 CE) show that this condition can also occur bilaterally (L’Abbé et al., 2008). And finally, Anderson (1963) recorded very high prevalence (8%) of bipartite patella in a Canadian Iroquois ossuary dating back to 1400 CE.
In modern populations, bipartite patella is usually discovered through knee radiographs. One of the studies involved analysis of the radiographs in Turkish patients in order to determine the prevalence of bipartite patella and analyze the differences between sex and laterality (Kose et al., 2015) concluded that there is a prevalence of around 1% of the condition being more frequently found in males, and mostly on the superolateral side. A similar study was conducted using magnetic resonance imaging (MRI) to determine the prevalence of bipartite patella and perform analysis of this rare condition (Akdag et al., 2019). This study confirmed that the condition occurs mainly in males and more frequently on the superolateral side, and that the overall prevalence is found to be 0.8% (Akdag et al., 2019). However, true prevalence of bipartite patella is still uncertain. Different authors reported different data: Green (1975) states that the prevalence of the condition is 0.2-6.0% while others say it may affect 1-3% of a population (Todd & McCally, 1921; Adams & Leonard, 1925; Tachdjian, 1990; Aufderheide & Rodriguez-Martin, 1998). There is a wide variation in prevalence in different ethnic groups, and sometimes high percentage can be the result of close kinship (Kose et al., 2015). Since the condition is mostly asymptomatic and a rare find in archaeological excavations, it is no surprise that a true prevalence can be difficult to determine.
Five other patellae from Malo Libinje show a condition called the vastus notch. This anatomical variant occurs due to continuous contraction of the vastus lateralis muscle of the femoral quadriceps (Capasso et al., 1999). It is associated with chronic knee flexion, i.e. squatting. Vastus notch appears as a slight or a deep concavity, frequently with the processus spinosus located at the inferior margin of the notch which marks the lower limit of the tendon (Oetteking, 1922). It is commonly mistaken for bipartite patella because it also occurs on superolateral side of the bone. The two conditions can be distinguished due to fact that vastus notch is smooth-edged (Mann & Murphy, 1990) as opposed to the porous surface with visible trabecular bone on bipartite patella. A separate ossicle can only occur if the patella is bipartite, detached or incompletely fused, and never associated with vastus notch. The pair of patellae (C and D) from G3 are especially interesting since the left one exhibits a vastus notch while the right one is bipartite.
According to the available bioarchaeological literature, vastus notch occurs a bit more frequent than bipartite patella. In Croatia it was recorded at several sites: the earliest example was observed on the right patella of an adult male from the Late Bronze Age cremation cemetery of Poljana Križevačka 2, dated to the 13th century BCE (Premužić, 2016); the second case was recorded again on the right patella of an adult male, this time in Glagoljaška Street in Zadar, dated to the Late Roman Period (Bedić, 2017). Another case was registered at the Sokol fortress in Konavle, dated to the Late Antiquity (6th century CE) (Topić et al., 2019). And finally, two cases were observed on the left patella of an adult male and the right patella of an adult female from Pakoštane – Maksanova gomila site, dated between the Late Middle Ages and the Early Modern Period (15th-16th century CE) (Šućur et al., 2020).
Opposite to bipartite patella, vastus notch occurs mostly due to repetitive activity. It is associated with chronic and consistent kneeling and squatting (Capasso et al., 1999). There are but few studies focusing on this lesion occurring in archaeological populations. For example, in a study of human skeletal remains from the early Neolithic settlement (10500-8400 BP) of Nemrik in Tigris Valley Molleson (2006) recorded the occurrence of small vastus notch in patellae of three individuals suggesting that the squatting on the heels could be a resting position, although the condition could also be induced by sartorial position. Furthermore, a small patella of a young female from the Neolithic settlement of Abu Hureyra in Syria displays vastus notch on the superolateral border suggesting that she as well as the other women from the group may have squatted in the ‘hocker’ position to carry out the certain tasks (Molleson, 2016). And finally, the study of various Islamic period skeletal assemblages from Medieval Iberia Habitual indicates that the adoption of praying resulted in patella alterations and development of vastus notch (Inskip, 2013).
Prehistoric people cultivated a whole range of domestic cereals which required mechanical preparation before they could be eaten. The preparation of grain such as grinding and dehusking was the most demanding and labor-intensive activity, and it usually took much time. Since the seed could not be kept once dehusked, the grain had to be pounded every day (Molleson, 2006). Repetitive activity of kneeling while grinding could have led towards chronic knee injuries. Frequent habitual activities of kneeling and/or squatting due to cereal preparation were surely practiced by prehistoric inhabitants of Kneževići – Malo Libinje and these could have resulted in high prevalence of vastus notch observed in this skeletal assemblage.
Today, few distinct defects associated with patella are acknowledged, some of which might be mistaken for bipartite patella and/or vastus notch (Figure 9).
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