Pondering These Knees
Most animal legs
will have some knees.
There’s also apes
And most of them all
have kneecaps, two.
the gnu, the shrew
and even frogs
have kneecaps too.
But NONE are found
on a kangaroo.
The patella, or kneecap, is one of the most incredible bones in your body. As a sesamoid bone, it is embedded within a tendon, where the quadriceps and patellar tendons meet. There, the rounded, triangular bone protects the knee joint and acts like a pulley, allowing the tendon to transmit more force with smoother motion.
Frogs may have evolved the first kneecaps. In 2017, researchers from Argentina discovered primitive, soft kneecaps in eight species of frog. “One implication of the discovery is that kneecaps like this began to evolve in the Devonian period 400 million years ago,” Andy Coghlan wrote for NewScientist.
Fun facts about animal knees
AUG 10, 201718036 VIEWS
1. All four-legged mammals have 2 knees and 2 elbows. That includes dogs, cats, elephants, horses – all quadruped animals. Their front legs bend exactly like our elbows. When talking about horses for example, the parts that we commonly refer to as knees are actually like wrists as the connecting joints can be more compared to human wrist than knees. That also means that the lower part of horse’s front legs is pretty much the same thing as our middle finger. Moreover, it is often believed that elephants have 4 knees, but this statement is false as elephants have similar bone structure as all other four-legged mammals, hence they have two knees and two elbows.
2. Bees have knees. Surprisingly, even such small creatures like bees have knees. Though they don’t have kneecaps, they have femurs and tibia similarly to human knees.
3. Grasshoppers and crickets have their ears on their knees. These „knee-ears“ are located on front legs and are so tiny that to this day it has been almost impossible to clearly understand the full functionality of these incredibly small yet capable set of ears.
4. The knees of cows and giraffes don’t bend well. Have you ever heard of the saying that a cow can go upstairs but not downstairs? There’s a simple explanation to that. The issue is that cows’ knees don’t bend much and they can’t raise their legs high, also they carry a lot of their weight on the back so going downstairs can be dangerous as they can just fall. So technically, they can walk downstairs, but it might result in getting an injury.
5. Birds’ knees are not seen – we see a joint that is actually comparable to human ankles. It is commonly thought that birds’ knees bend forwards, but the joint we see and get confused by is the section between tarsus and tibia. Bird’s knees actually bend the same way as ours but we just can’t see their knees as they are higher up, hidden by feathers.
6. Some reindeers have knees that make a clicking sound while walking. This knocking sound can be heard from great distances and is meant to help the reindeer herd stay together in blizzard.
7. Some big animals can sleep standing up thanks to a „lock“ mechanism in their knees. This system enables them to relax and rest with minimal efforts: a horse for example can stand even for years thanks to this amazing ability.
In some ways, animals are even more similar to us than we could imagine, yet the animal world is filled with strange and mesmerizing characteristics like these few listed above that illustrate perfectly how colorful the whole animal kingdom really is.
Absence of an osseous patella and other observations in Macropodidae stifle.
Holladay SD1, Smith BJ, Smallwood JE, Hudson LC.
The patella is a large sesamoid bone that typically develops in the tendon of insertion of the large extensor muscles of the stifle joint. Although present in almost all species of mammals and birds, it has been found to be absent in the red kangaroo and two wallaby species (family Macropodidae). In its place is a fibrocartilage pad, located in the tendon of the quadriceps femoris muscle. This structure is visible grossly, is palpable, and has the form normally expected of a bony patella. In addition, the femoral trochlea is shallow and asymmetric, and the lateral gastrocnemius sesamoid is unusually prominent. These and other related modifications in the area of the Macropodidae stifle are presented.