Abstract
The three-dimensional anatomy of the ostrich (Struthio camelus) knee (femorotibial, femorofibular, and femoropatellar) joint has scarcely been studied, and could elucidate certain mechanobiological properties of sesamoid bones. The adult ostrich is unique in that it has double patellae, while another similar ratite bird, the emu, has none. Understanding why these patellae form and what purpose they may serve is dually important for future studies on ratites as well as for understanding the mechanobiological characteristics of sesamoid bone development. For this purpose, we present a three-dimensional anatomical study of the ostrich knee joint, detailing osteology, ligaments and menisci, and myology. We have identified seven muscles which connect to the two patellae and compare our findings to past descriptions. These descriptions can be used to further study the biomechanical loading and implications of the double patella in the ostrich.
Highlights
Ostriches (Struthio camelus) are well known for their exceptional bipedal running abilities (e.g., Alexander et al, 1979)
We present an anatomical description of the morphology of the knee joint of ostriches, with a focus on features that are most relevant to the mechanics of the two patellae
Myology From our magnetic resonance imaging (MRI) scan and dissections of the knee region, we identified 12 distinct muscles that cross the knee joint near the patellae: M. ambiens part 1 (AMB1), M. femorotibialis intermedius (FMTIM), M. femorotibialis lateralis pars distalis (FMTLD), M. femorotibialis lateralis pars proximalis (FMTLP), M. femorotibialis medialis (FMTM), M. fibularis longus (FL), M. gastrocnemius intermedius (GIM), M. gastrocnemius lateralis (GL), M. gastrocnemius medialis (GM), M. iliotibialis cranialis (IC), M. tibialis cranialis- femoral head (TCfem), and M. tibialis cranialis- tibial head (TCtib)
Summary
Ostriches (Struthio camelus) are well known for their exceptional bipedal running abilities (e.g., Alexander et al, 1979). Their muscular, three-dimensionally mobile legs (Rubenson et al, 2007) are attractive subjects for studies of mechanical forces in the knee because they are able to accommodate large dynamic loads (Rubenson et al, 2011; Hutchinson et al, 2014). The knee joint sesamoid bones (kneecaps or patellae) in ostriches are of particular interest, because—unusually for birds and all other animals—they are present as double (proximal and distal) rather than single bones. This has been recognized for at least a century and a half (Macalister, 1864; Haughton, 1864), until recently the double patellar sesamoids of ostriches have been overlooked in a comparative context. Regnault, Pitsillides & Hutchinson (2014) showed that ostriches are unusual among ratite (Palaeognathae) birds in having these two patellae—emus and other ratites
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