Do Penguins Have Knees?

Unlike most birds, penguin legs are chiefly located within their body.

And so, they do have knees, only hidden beneath their muscles and feathers.

Therefore,

You may have to X-ray a Penguin to visualize its knees.

I wonder how the question even originated.

But even more puzzling is the idea:

Why are so many people interested in penguins having knees?

Then again, penguins seem to have a round body with protruding feet. 

It seems as if penguins lack legs altogether.

So, you may be curious

Does a Penguin Have Legs Or Just Feet?

A penguin has both legs and feet.

In fact, penguins have all those bones and structures present in any regular bird.

A penguin’s leg is also composed of femur, knee, tibia, and fibula 

 

But wait, where else do you think those feet get attached to?

Also, how do you suggest a penguin walks or bends without legs and knees?

You see, penguin legs and feet are slightly different than other birds. 

How so?

Well, this includes the following features:

  1. Unlike flighted birds, penguins don’t have hollow bones to reduce their weight. 
  2. Penguin pelvic bones are comparable to other birds. However, their femur is unusually short.
  3. Compared to other birds of relative size, penguins have long but fused tibia and fibula bones.
  4. A major portion of penguin legs along with knees is located within their bodies.
  5. The part of legs outside penguin bodies is essentially covered in thick feathers. 
  6. Penguins webbed toes with scaly thick muscle sheets, giving them the shape of swim fins.

While puffins have similar body shapes and feet, even they have legs outside their body. 

A more remarkable question would be to ask is, 

Why Do Penguins Have Short Legs And Webbed Feet?

Ornithologists associate these leg and feet adaptations for following benefits:

1. Conserving Body Heat

Most penguin species reside in the Southern Hemisphere, so they face freezing winds and snowstorms on daily basis.

Which is why

A penguin’s survival depends on its ability to resist heat loss.

Now, penguins have the following adaptation to conserve heat:

  1. Blubber- a fat coat underneath their skins.
  2. Feathers all over the body to trap warm air. 
  3. Huddling in colonies to reduce heat loss.
  4. Reduced body surface.

Now, penguin bodies are extremely packed to minimize heat loss through the skin.

This is further enhanced by the presence of limbs within their body.

More precisely,

Penguins conserve body heat by reducing their surface area through the evolution of legs and knees within their bodies. 

The portion of legs outside their main bodies is covered with thick feathers to lower heat loss.

Their feet can survive in extreme cold without getting frostbites. 

2. Enhancing Swimming Capacity

Penguins have extremely streamlined bodies designed for expert diving.

Even their limbs and tails are aligned to reduce water drag. 

Since large bodies experience more water resistance, therefore:

Long external legs would have increased water friction for penguins, thereby causing difficulty in swimming.

And, internal legs allow penguins to swim better.

Penguins are dependent on their swimming ability for food.

So much so that a penguin may spend up to 3/4th of its entire life living under the ocean. 

Swimming adaptability are crucial for a penguin’s survival.

As a result, penguins have wings adapted into flaps, and tails as rudders.

Another thing is penguin feet are shaped into swim fins to enhance their swimming ability.

3. Retaining Land-based Locomotion 

In Antarctica, land-based predators are almost non-existent.

While Skuas and Petrels do hunt baby penguins, they cannot eat adult ones.

That means,

Penguins don’t really need to walk much.

However, the short portion of legs outside their bodies enables penguins to walk through waddling.

More appropriately,

Having short external legs does not affect a penguin’s everyday life. 

Besides, penguins can cover long distances by sliding on their bellies.

This kind of movement is called Tobogganing.

Check the video to see how it looks

You may be thinking, 

“But Why Do Penguins Waddle And Not Walk Properly?”

Because for penguins, waddling is a more efficient way of walking.

You see, when an average human walks, then he walks by lifting about 78% of his entire weight with each step. 

Since a penguin has short legs, walking like a human will cost it more energy. 

So, instead of lifting its entire weight, a penguin walks by rotation.

So, a penguin lifts its foot and rotates forward.

It does the same with its other foot, thereby taking a step further. 

This is exactly how a pregnant woman gets to walk. 

But, did you know penguins can waddle on their toes?

Apparently, this reduces heat loss as penguins reduce exposure to icy crust beneath their feet. 

Penguins warm their babies by holding them above their feet.

And so, penguin toes play a crucial role in incubating eggs as well as keeping the penguins alive in Antarctica. 

Speaking of penguin toes, have you ever wondered:

Do Penguins Have Fingers?

They do at least have the finger bones.

Now, penguins use their feet to navigate through water, hold their babies, walk and even stand on the ice.

So, it’s no wonder that they can move their toes individually within their feet.

However, penguins don’t use their wings for anything but swimming. 

You see,

Penguin wings are designed into flippers exclusively for swimming and diving.

The bones within these flipper-like wings are broad, flattened, and sturdy.

The joints are fused together to reduce damage by water pressure while swimming. 

For this reason, even the penguin wrist bones are fused into radius and ulna bones. 

The edge of a penguin flipper is composed of bones from the first and second phalanges (See figure 2).

Penguins do have bones for the index and middle fingers. 

Figure 2: Penguin Wing Bone Structure

Animated by SeanHyatt (Taken and modified)

However, even finger bones are fused together to form a single bone.

That said, penguin wings are quite short for their body size.

Also, they don’t seem to have any joints within.

So, you must be wondering:

Do Penguins Have Elbows?

They certainly do.

While penguin elbows are located outside their bodies, however, these bones are completed fused together to allow little to no movement.

And so, penguins move their wings through the contraction of pectoral muscles on the ball and socket shoulder joints.

Still, penguin wings have their distinct shape because of their elbow bones.

But,

Why Do Penguins Have Fused Elbows?

Now, flying birds adjust their wingspans through elbows and shoulder muscles.

However, penguins don’t fly and so, they don’t have flight feathers to adjust.

Penguins swim in water as birds fly in the air.

But water is about 900times denser than air.

If a penguin had joints in its limbs, the water pressure may be enough to break its bones.

Therefore,

Fused and heavy elbow bones protect the penguin wings from snapping.

This is also why penguins’ knees are located within their bodies.

Otherwise, they would have broken up during evolution.

Outwardly, it seems as if penguins don’t have knees and yet they do.

But,

What Animals Don’t Have Knees? 

Nearly, all animals with legs have knees.

So, animals without knees would include certain 

  1. Invertebrates 
  2. Reptiles like snakes
  3. Fishes. 

However, even insect legs function as knees do. 

So it boils down to

How Do You Define a Knee?

If by knee you mean, a leg-like appendage then, most land animals have knees.  

However, if a knee is something with a joint and a knee cap.

Then, 

Birds like Emus and Cassowaries do not have kneecaps, and therefore, do not possess true knees. 

Nobody can say for sure how the absence of knees can help these birds adapt better.

Still, these are considered birds of ancient origin.

Interestingly, ostriches have two kneecaps on each leg. 

Again, it is unclear how having two knees per leg helps ostrich in walking.

Wrapping Up 

Penguins do have legs and knees but within their bodies.

The short legs and arms help penguins be better swimmers and conserve more body heat.

While penguins do have finger bones, but these are fused together.

The same is true for their elbows

All legged animals have knees or similar appendages.

Among birds, cassowaries and emus don’t have kneecaps.

Meanwhile, ostriches have two knee caps per leg. 

Here’s some related articles about penguins which you may find interesting

Can penguins fly?

Are penguins friendly to humans?