by Matthew Cobb
All tetrapods have kneecaps, although it appears that they evolved more than once. Even tuatara have kneecaps (it was long thought they did not). And here’s a kneet biomechanics demonstration of why they are so useful, and what you can and can’t do without them.
https://twitter.com/PainSci/status/702601079792410624/photo/1
Reblogged this on The Logical Place.
So what happened to my elbow-caps?
That was my immediate thought too, but you beat me to it.
cr
The patella is as much about joint protection as it is about leverage. Our weight-bearing, forward-facing knees desperately need protection, our backward facing elbows much less so. Unless we play certain sports, in which case we strap on elbow pads.
A very effective little demonstration.
And so helpful….especially for those of us with AKS (Ageing Knee Syndrome).
So that’s what they call it. Probably some osteoarthritis and age related deterioration. There. Now I feel so much better. 😎
Clearly given to us by God. . . 🙂
I’ll take option 1 (no kneecap) thanks. It might be *way* less efficient, but it means you won’t be screaming in pain when the pesky thing pops around the side in the middle of a basketball game.
Sub
Surely the benefit being illustrated is actually a result of the ‘muscle’ acting on a longer lever (because it runs over the ‘cap’), whereas in reality the muscle does not do that… So that doesn’t explain why we have kneecaps surely?
That’s what I was thinking.
Bones are connected to muscles via tendons. Even if the demonstration doesn’t exactly conform to human anatomy, the principle is correct: It improves the moment arm of the tension elements in extension of the lower leg.
We have a quadriceps tendon that attaches the quadriceps muscle to the top of the patella and a patellar tendon that connects the patella to the tibia on the bottom…so pretty similar, even though the tendons don’t go over the patella. This system straightens out your leg.
Barnowl can come along and correct me if she likes. 🙂
Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.
– Archimedes
Long ago when I had a bicycle but no car, I became adept at using bungee cords to secure big loads on the bike. Which prompted a friend to observe, “Give me a bike and enough bungee cords and I’ll move the world.”
Most modern day Tetrapods including our Avian Therapod Dinosaurs (Birds)have them , but most Reptiles do not. Non Avian Dinosaurs didn’t have them, and it may be because it was a “floating” Bone it leant itself to easier Evolving or Devolving.
Except that there are no tendons running over the top of the kneecaps. Leg muscles don’t work that way.
The principle is correct: The patella improves the moment arm of the tendons that extend the lower leg. The demonstration isn’t exact; but near enough. The load will go as close to the anterior surface of the patella as the individual anatomy will allow.
As a long-time mechanical engineer, I Approve That Message.
Following an accident in childhood, my right knee cap is split into two parts. Kneeling is torture.
“Kneeling is torture.”
Ive been to some Catholuc services. They are torture even without the kneeling.
I’ve had to go to a Catholic service a number of time with some of the extended family. I simply refuse to kneel. If it hurts, even a bit, why the hell should I? Why should I if it doesn’t hurt?
Sweet demo!