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Let's tackle the easiest tendon

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in the foot, the achilles.

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It's the largest, it's the longest,

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10 to 15 centimeters in length.

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And it's made up of the confluence

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of the soleus and the gastrocnemius.

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It's surrounded by a fibrous

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sheath known as paratenon.

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There's no synovium around it, so

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there's no true tenosynovial sheath.

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And the anteroposterior dimension

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is usually about 7 to 8 millimeters.

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The achilles tends to be a

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little bit convex posteriorly.

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It shouldn't be semilunar or convex anteriorly.

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In other words, the achilles

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shouldn't have a shape like this.

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And the achilles usually travels with a

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small tendinous unit, anteromedial to it 90

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percent of the time, called the plantaris

0:50

tendon, which is sometimes used for, um,

0:55

Now let's talk a little bit about the

0:56

relationship of the soleus and the gastrocnemius.

1:00

Let me, uh, do a little drawing here.

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So here's the gastrocnemius.

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We'll make the soleus in blue.

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And that would be one half of the achilles.

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And then the other half is

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gonna look similar to that.

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You've got these two muscles

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that are traveling together.

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Forming two bundles.

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So we would have basically a duplication of this

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for the second bundle, so let's draw it again.

1:29

We would have the soleus in blue,

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and then we'd have the gastrocnemius

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in yellow on the other side.

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And then these two would come

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together to form one unit.

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Now, I don't really care so much about

1:43

this medial-lateral relationship, because

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as you go down, these things are gonna

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kind of twist and spiral around one another.

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So, memorizing that, not really critical.

1:55

What is more important for you to

1:56

memorize is the relationship of the soleus

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as we go from proximal to distal.

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So let's start up high.

2:05

We've got muscles.

2:07

We've got an intratendinous achilles.

2:10

Sorry, an intramuscular achilles.

2:12

And then on the T1 we see

2:14

the myotendinous junction.

2:16

And right after that, about 5

2:18

centimeters above the superior calcaneal

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protuberance, is the watershed area.

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In the watershed area, you've got hypovascularity,

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this is where a lot of ruptures will occur.

2:31

Then we've got the belly of the tendinous

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component, a small recess, which sometimes

2:37

has a little bit of fluid in it, not

2:39

to be confused with a slit-like tear.

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This is normal, about one to two

2:43

millimeters of fluid may sit in the

2:45

retrocalcaneal space, in this little recess

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between the achilles and the calcaneus.

2:53

Then as we get a little further

2:54

down, we start to see the achilles

2:57

tightly attached to the calcaneus.

2:59

And this is its footprint, the upper,

3:02

deeper portion of the footprint.

3:04

I'm going to draw on it right now.

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And I'm going to use the color blue. Upper and

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deeper in here going to be mostly made up of

3:13

soleal fibers, the more inferior and superficial

3:19

component here is made up of gastroc fibers.

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And sometimes these will actually separate.

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So you might have fibers that are preserved

3:31

deeply, that attach over here, and fibers

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that come off over here and retract all

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the way up, and leave a little preserved

3:39

area of soleal fibers in the front of it.

3:42

Or separate the soleal fibers from the

3:45

gastroc fibers and this is a type of

3:48

delamination separation type of tear.

3:50

And that's the reason why it's important to

3:52

understand this sort of layering effect that

3:55

you get as you go a little bit more inferior.

3:58

Just one other side note, and that is when

4:00

you're looking at the achilles, you should

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always pay careful attention to the shape and

4:05

configuration of the posterior superior calcaneus.

4:10

But this is where the pump bump or Haglund

4:12

deformity will form, and it's usually seen most

4:15

prominently in the posterosuperomedial calcaneus,

4:20

often associated with high heel wearers.

4:23

That includes our introductory

4:26

discussion of the achilles.