13. Pelvic Tilt & Gusset Mapping
How To Account For Anterior/Posterior Pelvic Tilt
This article is based on a discussion that took place in our Facebook group. From time to time great discussion topics come up that really need to be preserved so we stick them in here for everyone's reference. If you want to read the full thread and contribute to the discussion then you'll need to join the group. The original unedited thread is located here:
Gusset Mapping – What is it? Well it's about locating, on a pattern, all the changes in shape from waist to waist through the crotch ... where they start and stop and at what angle to the front and back. Over the years a basic one piece block has developed that fits pretty much most normal people (ok there really isn’t any such thing as normal) and most pattern makers only need to care about the width of the crotch at the narrowest point. Well this is fine if they get the angle of the leg hole and the section around the front tendons right first, if not they need to make the crotch width narrower to compensate for this error.
So what you end up with is each designer has their favorite leg hole design and then they find what crotch width works for that and stick with it. They rarely measure this and every single one of them will tell you exactly how much crotch width is ... irrelevant of the garment use.
The trouble is that most people don’t realize that the narrowest part of the garment and the narrowest part of the anatomy don’t always line up on their pattern. If the neck (the narrowest part) is too far back and too wide you get baggy butt. If the neck is too far back and too narrow the wearer pulls the garment higher and you get hungry butt. If it’s too far forward and too wide you get a different type of baggy butt. If it’s too far forward and too narrow the front of the garment rides too high and you get camel toe (also exacerbated by people trying to shorten it too far forward of the neck to compensate). I’ve seen it all. If your garment doesn’t match anatomy then you’re going to have problems.
The most typical of all is too far back and narrow. I make this misjudgment quite often myself when trying to narrow as far as I can in Brazilian center back seam styles where I need to shorten the bottom of the back panel (narrow strips stretch more so you need to shorten them). It’s easy to mess up, but easy to correct after testing. Unfortunately I believe more than half of the PDF patterns out there have this problem. Besides the hungry butt there’s another tell-tale sign in the front …. It looks like it’s bunching up over the tendons. This is because the back is trying to pull the front through and keeps going until it locks up on the tendons. The first reaction people have is to make the gusset narrower which only makes matters worse … you actually need to make the gusset longer!
Anyway … more on technique after. Let me give you some background that might help with better understanding the issues first. There’s this thing called anterior pelvic tilt. Many, many years ago a lady hobbled into my shop ... this was how it all started ... because when she came to me she was using a walker to stand up ... she was only 22 years old and she’d grown up with a spinal disorder. Her doctors wanted her to swim as part of therapy but she couldn’t get a swimsuit to fit her shape because her hips were extremely rotated forwards. She’d even brought me a referral letter from her doctor because apparently no seamstresses understood what was going on well ... the letter didn’t help me understand anything from a swimwear perspective so I called him and asked if he had any models or documentation I could read. Well he was very pleased I was taking him seriously and made an appointment to show me what he had. He had every image and plastic model imaginable. He was happy to give me a few hours of his time to explain it all and show me movement issues ... I also went to their physiotherapy center where they showed me the pool and the issues the patients had. I was able to see and talk with people with varying conditions who were all happy to talk to me ... they really wanted me to understand the problem.
At first I was looking at what I though was short front panel with an extra long back panel being needed. Anterior pelvic tilt comes from a number of different medical conditions but beyond the extreme rotation of the pelvis the patients can experience all sorts of bone and muscle pain from unusual wear and tear of things simply being in the wrong place.
So back to the doctor’s office I went to examine the models in the light of what I’d seen. I literally draped paper over the models, scaled them up and compared them to normal and it became obvious what was happening. In extreme cases we were looking at a pubic bone that might usually sit proudly out front, being in between the legs. In some cases, the patients ‘anatomy’ was so far posterior that the cheeks were now collapsing over it. Suddenly I stopped seeing the gusset as being in a specific position relative to the legs and realizing it moved backwards and forwards with varying pelvic tilt ... and as it moved back or forth it changed shape and width!
Anyway, armed with this information I made my very first medical swimsuit ... the very first try at a one piece I made fit so perfectly I had everyone at the physio center asking me for custom made garments on the spot .... these were women who saw me accompanied by a doctor were also used to having anatomy examined so it was not unusual for them .... that allowed me to test and do the further research I needed to understand it all.
I made little cardboard models of what were essentially crotch cups they could place over their G string themselves (they couldn’t wear normal panties obviously) and find which shape fitted them the best. This got so many laughs from everyone and in hindsight it must have looked insanely crazy, but this was all I knew how to do in my limited experience as a young designer back then ... they trusted me because I’d already got some great results.
So they took a handful of cardboard models into the change room and came back with their selection ... from the cardboard model I could draw the map with their sizes. Now I had something to study and I could see what was happening to the shape of the crotch as the pelvis gradually tilted further and further. I never had to touch anyone beyond the few normal measurements we’d take as pattern makers.
Now here’s the thing ... the same theory applies to everything.
Exotic dancers, for example have full tension on tendons the majority of their routine because they’re deliberately trying to exaggerate the arch in their back. This means overly developed muscles at the front and full on pelvic tilt, not to mention the highest possible heels adding to the mess ... all this usually pulls g strings up and forward exposing things they aren’t yet ready to expose ... the entire gusset (well sort of gusset in a G string) is moving towards the front with every step. Exotic dancers are rolling hips intentionally during a routine, not like normal dancers.
So how do we know what is normal? How do we measure tilt? Well it’s easy ... look at the back, not the pelvis ... are they over arched? We all know what an arched back looks like? We all know how heels exaggerate things. Look at the images below ...
The first bit of good news is that it's harder to understand what the problem is than it is to fix it ... or is that it's easier to fix it than it is to work out what's going on ...or ... forget it, I'm just confusing myself. ... moving on ...
Have a look at the first image below. What you're looking at is varying degrees of tilt from 10 posterior to 20 anterior. I've seen as much as 35 anterior, but I doubt greatly you're likely to experience any more than 20 degrees anterior where things start to get a little more complicated.
Up to 10 degrees posterior is something you may well see in classical ballet dancers who've trained for some years already ... but generally you can accommodate up to that much by doing the simple things outlined at the end. These dancers torture themselves in training to make dancing look effortless!
Up to 15 degrees anterior tilt is something I frequently saw making costumes for professional exotic dancers who wore heels all day just to train themselves ... I can't imagine anything more painful (besides listening to the word seamless being used incorrectly) so if you ever feel like looking down on them think again ... some of these women are as strong as professional athletes!
Ok looking at the diagram. The red line represents the position of the pubic bone ... the green line represents the tendon position. As we were saying in part one, the pubic bone can move right between the legs in extreme cases of pelvic tilt. Normally it's just forward of the tendon position. I use the pubic bone position as an indicator of how much tilt I have. The top of each diagram is the waist line ... the pubic bone obviously doesn't change position relative to the front waist but the back can so finding the natural waistline on someone with severe anterior tilt can be difficult.
The blue line represents the position of the crotch or gusset seam ... it's also about the position of the anus.Notice that the angle between red and blue lines don't change. What we're seeing from a pattern point of view is not so much the pelvis rotating, but the position of the tendon moving ... ie, the pelvis isn't so much going between the legs, but the legs are angling forwards ... this is literally how it is for exotic dancers for example.
AND the position of where the cheeks start between the legs is determined by the legs, not the pelvis, so this line moves along the the gusset with rotation of the pelvis too!
There are a few other things happening too. With increased rotation to the anterior the cheeks do appear to rise relative to the body, but not as much as the pelvis rises, so technically the cheeks are moving more over the anus. One thing I learned from the doctor was that in severe cases the cheeks can move so far relatively toward the front and the muscles so stretched and hard that things like normal sex become almost impossible too ... sounds odd but it was something that the patients talked about when it came to wanting lingerie made too!!!
Another change was a hollow that occurred where the cheeks started which was longer than normal. This doesn't affect normal patterns but it's of interest when making G strings (the end of the G string needs to be longer and wider - another exotic dance issue)
OK So how do we accommodate this in the pattern?
Take a look at the image below . I've split the band in half on each side and rotated the sides down and open 5 degrees for every 10 degrees of tilt (or up and closed for posterior tilt). This helps the band sit flatter on the tummy and prevents a strange gaping phenomenon that occurs when the tendons angle inward and pinch the entry into the gusset. It also helps angle things in the next step.
Next we cut the front horizontally along where the normal public bone would be and at the back gusset seam and move the whole gusset section up. How much is something I've developed a rule of thumb for that isn't an exact science but a staring point I move it up 1.5% of hip measurement for every 10 degrees of tilt ... eg; 1.5% of 89cm hips would be 1.33cm ... or say 2cm for 15 degrees of tilt and so on (I don't use waist to waist anymore like you'd expect because it doesn't seem to be as proportional). The same applies in reverse for posterior tilt. The curved blue lines are how we re-curve the leg line around the tendons ... we line up to the band end, not the gusset end. Note: many people would look at someone with 5 to 10 degrees of tilt and just see bunching in front and think the crotch width was too wide, but that width is fine and the leg tendons are in the wrong position relative to the narrowest part of the crotch ... so they'd narrow the crotch and little would happen, so they'd keep going until they cleared the tendons and suddenly get hungry butt show up! Pattern maker meet rabbit hole, rabbit hole meet pattern maker.
Now the green line is also important ... we need to maintain the maximum width of each design (as it was intended by the designer) as we have more width of cheek with more pelvic tilt. The only consolation is that with serious tilt there's significantly less movement so less risk of things falling off .... but don't count on it ... and it's harder for these ladies to adjust themselves!
Anterior pelvic tilt does lend itself well to a fitted center back seam ... in fact it's the best thing you can do to create an attractive aesthetic. Instead of cutting a few sections to rotate to create the curved seam you cut an extra one slightly higher up to create more curve ... it's literally like making a bra cup for each cheek!
The above image shows ...
Blue - 20 degrees anterior
Red - 10 degrees anterior
Black - normal
Green - 10 degrees posterior
... relative to each other. All the same size waist, waist to waist and hips but subtly different patterns to achieve exactly the same style on the body.
This is the basic concept and a good thing to keep in mind. It does get more complicated with narrower back panels which can suddenly collapse into hungry butt (there must be a proper technical term for this) because the shape of the cheek drop and open more with tilt.
Absolutely none of this is about the width of the crotch but whether it is too far back or forward! Yes you can make crotch width too wide or narrow, but to presume a fitting issue is a crotch width problem without first checking pelvic tilt is a recipe for disaster .... and this is the point I wish to make here ... you may well have a crotch width issue the majority of the times, but if you see something that makes you think you have a crotch width issue then check pelvic tilt first.
Let me explain ... let's assume a pattern maker creates a new style for RTW and tests it on a model only to see bunching fabric over the tendons. Most pattern makers would go straight in and narrow the crotch. But if the model had, say 10 degrees of anterior pelvic tilt because she was wearing 4" heals at the time of the fitting (don't laugh I've seen it more times than I care to mention) then the pattern may well have been correct originally, yet the pattern maker has now sent a garment that's too narrow into production ... which then doesn't sell as well.
Now here's the next catch ... if you are doing a RTW fitting on a model and the garment looks perfect, don't just smile and be happy and move on to the next garment ... you still need to check the model for pelvic tilt, because if she has it and the garment sits beautifully then it's incorrect for RTW!!! Get it? Check for pelvic tilt every time you do a fitting.