The Anatomy of a Stitch: The Science of Knitting
I’ve been working on a new bandana scarf pattern recently, using a mix of garter stitch and moss stitch. As I was knitting, something struck me: moss stitch is essentially just knitting knits and purling purls—very similar in rhythm to garter stitch—and yet the finished fabric looks quite different.
That small shift in how knit and purl stitches are arranged changes the texture and drape of knitted fabrics, despite utilising the same two stitches.
It really highlights something we don’t always think about: knitting is less about what stitches you use, and more about how they sit and interact. Once you understand what a stitch actually looks like—on the needle and in the fabric—you start to see why these differences happen.
What a Stitch Looks Like on the Needle
Before a stitch becomes fabric, it sits on your needle as a loop—and that loop already has structure.
Each stitch has two legs:
- a front leg (closest to you)
- a back leg (furthest away)
In standard Western knitting, the front leg sits slightly forward and to the right. This is the leading leg, and it’s the part your needle usually enters when forming a stitch.
When the stitch is mounted this way, it’s open and untwisted, which allows it to form a balanced, even loop. Change that orientation, and you change how the stitch behaves—this is where twisted stitches come from, and why they feel tighter and less flexible.
So even before you knit or purl, the stitch already has a direction and structure that matters.
Forming a Knit Stitch: The V at the Front, the Bump at the Back
When you knit into a stitch, you’re pulling a new loop from the back of the work through to the front.
Once that loop is formed and the old stitch drops off, something very specific appears in the fabric:
- On the front, you see the familiar V shape
- On the back, there’s a horizontal bump
That bump is the loop of the stitch you just worked into - it’s just sitting on the reverse side, out of view when you’re looking at the knit side.
So every knit stitch actually contains both elements:
- a V on one side
- a bump on the other
You’re simply choosing which side faces you.
Forming a Purl Stitch: The Reverse View
When you purl, you’re doing the same thing—but in reverse.
You pull the new loop from the front of the work to the back, and that flips what’s visible:
- On the front, you now see the horizontal bump
- On the back, there’s the V shape
So a purl stitch is not a different structure—it’s the same stitch viewed from the opposite side.
And it’s also why the two stitches feel so different to the touch. The purl side has those raised bumps sitting on the surface, giving it a more textured, slightly “grippy” feel.
The Full Anatomy of a Stitch
Now that you can see both sides, the anatomy becomes much clearer.
Each stitch is made up of:
- a loop – that sits on the needle (this forms the bump on the next row)
- two legs – creating the V shape
- and the bar (running thread) – the horizontal strand connecting stitches side to side
That running thread is especially important. It holds a small amount of slack yarn, which allows stitches to move and shift slightly. This is what gives knitted fabric its flexibility and drape.
So each stitch isn’t static—it’s a small, flexible unit that can open, tighten, and redistribute yarn depending on how the fabric is used.
How This Creates Different Fabrics
This is where everything starts to come together.
Because every stitch has both a V side and a bump side, the fabric you create depends entirely on which side is facing out, and how those stitches are arranged.
Stocking (Stockinette) Stitch
In stocking stitch, you knit every stitch on the right side and purl every stitch on the wrong side.
This means:
- All the V shapes line up on the front
- All the bumps sit on the back
The result is a smooth, uniform surface—but also an unbalanced one. All the stitches are oriented the same way, which is why stocking stitch curls. The structure is pulling consistently in one direction.
Garter Stitch
In garter stitch, you knit every row.
But because you turn your work each row, you’re alternating between:
- rows where you see the V side
- rows where you see the bump side
This creates those familiar ridges.
More importantly, it balances the structure. The opposing orientations of the stitches cancel each other out, which is why garter stitch lies flat and feels springy.
Moss Stitch
Moss stitch takes things a step further by alternating knit and purl stitches both across the row and between rows.
So instead of rows of Vs and rows of bumps, you get a scattered mix:
- a V then a bump
- the reverse on the next row - bump then V
This breaks up the structure completely. There’s no continuous line of stitches pulling in one direction, which is why moss stitch:
- lies flat
- has a dense, textured surface
- almost looks woven rather than knitted
This is exactly why it looks so different from garter stitch, even though both use knit and purl stitches throughout.
Ribbing
Ribbing organises stitches into vertical columns.
For example, in a 1x1 rib:
- knit stitches stack to form columns of V shapes
- purl stitches stack to form columns of bumps
These columns behave differently. The knit columns want to pull inward slightly, while the purl columns push outward. This interaction creates elasticity, allowing ribbing to stretch and then spring back into place.
That’s why ribbing is so effective for cuffs, hems, and necklines.
Why This Matters in Practice
Once you understand that every stitch has both a V and a bump, a lot of knitting suddenly becomes easier to read.
You can look at your fabric and immediately recognise:
- where you’ve knit
- where you’ve purled
- whether a stitch is sitting correctly
- or if something has been twisted or worked incorrectly
It also helps explain why small changes—like swapping a knit for a purl—can completely transform a fabric. You’re not just changing a stitch, you’re changing which part of that loop is visible and how it interacts with the stitches around it.
Stretch, Movement, and Ease
All of this structure also explains why knitted fabric behaves the way it does when you wear it.
The yarn itself might not stretch much, but the loops can move. The bars between stitches redistribute yarn, the loops and legs shift slightly, and the whole fabric adjusts under tension.
That’s what gives knitting its natural elasticity and comfort. It’s not just soft—it’s structurally flexible.
Closing Thought
Every stitch you knit contains both a V and a bump. Every fabric you create is simply a different arrangement of those two elements.
Once you start to see that, knitting becomes much more intuitive. You’re no longer just following instructions—you’re shaping a fabric, one loop at a time.
FAQ: Knit and Purl Stitch Anatomy
What is the difference between a knit stitch and a purl stitch?
A knit stitch and a purl stitch are actually the same loop, just viewed from opposite sides. A knit stitch shows a smooth “V” shape on the front, while a purl stitch shows a horizontal bump.
Why does a knit stitch look like a V?
When you knit a stitch, the legs of the loop sit at the front of the fabric, forming a V shape. The curved top of the stitch (the head) sits at the back, which is why you don’t see it from the front.
Why does a purl stitch look like a bump?
A purl stitch brings the head (or crown) of the loop to the front of the fabric. This creates the small horizontal bump that gives purl stitches their textured appearance.
Is the back of a knit stitch the same as a purl stitch?
Yes. The back of a knit stitch looks exactly like the front of a purl stitch, and vice versa. This is why knit and purl are often described as two sides of the same stitch.
Why does stockinette stitch curl?
Stockinette stitch curls because all the knit stitches face one side and all the purl stitches face the other. This creates an imbalance in the structure of the fabric, causing it to roll toward the knit side.
Why doesn’t garter stitch curl?
Garter stitch alternates between rows of knit and purl (because you turn your work each row). This balances the structure, preventing the fabric from curling.
What is moss stitch and why does it look different?
Moss stitch alternates knit and purl stitches both across rows and between rows. This breaks up the structure of the fabric, creating a textured, almost woven appearance rather than smooth rows.
Why is ribbing stretchy?
Ribbing creates vertical columns of knit stitches (Vs) and purl stitches (bumps). These columns behave differently and pull against each other, giving the fabric elasticity and stretch.
How can I tell if a stitch is knit or purl?
Look at the front of the stitch from where it was worked:
- A V shape = knit stitch
- A horizontal bump = purl stitch
When viewed from the back, these will be reversed.
Learning to recognise this makes it much easier to follow patterns and fix mistakes.