Is the knee locking mechanism present in animals?
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