Looks like the bird world's most famous celebrity star has funny bones.
Ostriches have long been known to be the largest living bird species and those laying the largest eggs of any bird alive. They even hold Guinness World Record for these. However, they also have another amazing feature others may not know about--their unique leg kneecaps.
It has been known since 1864 that ostriches actually have two kneecaps in each leg. But the reason for it still remained a mystery ever since. Now, we may just have the answer thanks to researcher Sophie Regnault and her colleagues at the Royal Veterinary College in London.
Utilizing an imaging technique called biplanar fluoroscopy, they tracked the bone movement of a donated dead ostrich. With this, they built a simple model to understand the effect of the kneecaps on the leverage of the knee extensor muscles.
“The upper kneecap looks similar to the single bone in ourselves and other animals,” says Regnault. However, “the lower one is very closely attached to the lower leg bone… a bit like the point of your elbow.”
Kneecaps usually improve leverage of the muscles controlling the knee to lessen the amount of force needed to straighten it. “It’s a bit like putting the door handle further from the hinge,” says Regnault. “It requires less force to open the door.”
But ostrich kneecaps seemed to do the opposite. “The upper kneecap actually seems to decrease the leverage of the knee muscles, not increase them,” says Regnault. This might sound straight-out disadvantageous but researchers say this could also enable them to straighten their leg more quickly whilst needing more force.
Hence, the cost may be worth it as this allows them to run quickly. The lower kneecap (the one most species don’t have), on the other hand, may be shielding the joined tendons crossing the front of the knee.
The accuracy of this explanation, however, isn't certain as there are no other "double-kneecapped" animals to compare with.
Well, evolution, man.
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