We study in human anatomy that when the knee is in full extension, the femur slightly medially rotates on the tibia to lock the knee joint in place. This reduces the work required to be done by the hefty thigh muscles. This happens in the knees in humans since they are the weight bearing joints.

So, is the mechanism of locking present in other animals? If yes, is it even in the fore limbs or just the hind limbs?

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    $\begingroup$ Could you please paste in a link here? of an appropriate result? @Fang $\endgroup$
    – Polisetty
    Mar 16, 2016 at 21:54
  • $\begingroup$ en.wikipedia.org/wiki/Stifle_joint Equids use this stifle joint to stay standing while they sleep. $\endgroup$
    – White Fang
    Mar 16, 2016 at 21:58
  • $\begingroup$ @fang thanks a lot! It happens to be similar to humans, the mechanism. But locking happens only in the knees in bipeds. This makes sense since our liwer limbs are the ones that are wt bearing. is there a similar mechanism in quadrupeds in their fore limbs as they too are weight bearing. $\endgroup$
    – Polisetty
    Mar 22, 2016 at 19:19

1 Answer 1


Yes, the mechanism of patellar locking does occur in quadrupeds too. Although they are 4 limbed, a major portion of the weight is borne by the hind limbs. This is known as the stay apparatus and includes the mechanisms of Patellar locking, reciprocal mechanism and check apparatus.

On the other hand in the forelimb, although there is no locking mechanism as such, there exists a neat difference from the human anatomy. Human forelimbs are majorly adapted for manipulation but for quadrupeds, they are weight bearing. There exists what is called the stay apparatus - which includes the suspensory apparatus and the check apparatus.

For a detailed explanation for the interested reader, heres a helpful link - https://en.wikivet.net/Stay_Apparatus_-_Horse_Anatomy


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