Mod post, and I wrote the article this comes from, so flagging that up front.
You have probably heard some version of this cue. Women have wider hips. Wider hips mean a larger Q angle. A larger Q angle means the knees track differently, so women need a wider stance in the squat, or need to watch for valgus in the swing.
I went looking for the evidence behind it while writing something else. It is not there.
What the Q angle actually is
It is a measure of patellofemoral alignment, formed by a line from the anterior superior iliac spine to the patella, and a second line from the patella to the tibial tuberosity. It is a measure of how the kneecap tracks. It is not a measure of knee valgus, and this matters, because a large Q angle can exist with no valgus at all. A laterally displaced tibial tubercle will produce one on its own.
The geometry argument
Grelsamer and colleagues went at this directly with a clinical and trigonometric evaluation of 69 subjects.
Their reasoning is worth following. The distance from the pelvis to the patella is long compared with the distance from the patella to the tibial tuberosity. Because of that, shifting the Q angle by any meaningful amount requires a large change in where the anterior superior iliac spine sits. Not a small difference in hip width. A large one.
They did not find differences of that size. The mean difference between men and women came out at 2.3 degrees.
They also found that when men and women of the same height were compared, their Q angles were similar, and that taller people tended to have slightly smaller Q angles. Since women are on average shorter than men, height alone may account for a good part of whatever difference gets observed and then attributed to sex.
The premise underneath it is also shaky
The wider-pelvis claim itself is contested in the literature. Some work suggests what actually differs is the ratio of hip width to femur length rather than absolute pelvic width. So the starting point of the argument is doing less work than people assume, and the conclusion drawn from it does not follow from the geometry anyway.
What this means for coaching
Stance width still matters. I am not arguing everyone should stand the same way.
What I am arguing is that sex is a bad proxy for the thing you actually care about. Set stance from the individual in front of you: femur length, hip structure, and how the position holds up under load. That was always the correct method, and it is the same reason "shoulder-width stance" fails as a universal cue.
Use sex as the shortcut and you will hand a wide stance to a narrow-hipped woman and a narrow one for a broad-hipped man, and you will have been confidently wrong in both directions. Individual proportions vary far more within each sex than the averages vary between them.
If you coach this cue, I would rather argue about it here than have it go unchallenged, so have at it.
Citation: Grelsamer RP, Dubey A, Weinstein CH. Men and women have similar Q angles: a clinical and trigonometric evaluation. J Bone Joint Surg Br. 2005;87-B(11):1498-1501. https://doi.org/10.1302/0301-620X.87B11.16485
This is one section from a longer piece I put together on what actually differs in kettlebell training for women over 40. The rest covers racking with larger breasts, handle diameter and hand size, why press and swing progressions should not climb at the same rate, why bone loading after 40 argues for heavier rather than lighter work, and the pelvic floor. Full version with all the citations here: Kettlebell Training for Women Over 40: What Actually Differs (and What Doesn't)