jzamp, with respect to the article of Chemist's you cite, couple of things to think on:
1) It's one article. Science depends on replication of results. As far as I know, it's not been replicated. It's done using anthropometric instruments, which have a low accuracy, even with a high replicability. Data from human skeletons, which are the basis for forensic identification of sex in court, show systematic sex differences even at the same stature. The sample you cite is from folks at an orthopedic clinic, which means it's a biased sample; they're injured. Subjects were were standing, static, not moving. As you'll see in a moment, dynamic analyses show a very different result. The correction for height is not a true correction for scale, which has a more complex mathematical relationship with the skeleton, this has been discussed widely since the 1920's. And the authors note that some of their landmarks that did not show sex differences, such as diameter of superior anterior iliac spine, "might clearly be different" if the lateral aspect of the spine were measured. Eg, they picked landmarks that have been previously known not to show a significant sex difference. So they found little sex difference after a simple correction for size. Interesting, but not unexpected, and not a refutation of all previous work.
2) It helps to think about the skeleton as a scaffolding for insertions and attachments of muscles that create movement. The biomechanics can be quite complex, especially at the knee, which is a kind of sliding hinge that can also rotate. So I tend to use terms like "femoral angle" as a shorthand for a large number of small to moderate sex differences in the architecture of the hip, femur, and knee that create even more functional differences in how male and female bodies move in space, and react to loads. For instance, a slight sex difference in the origin and angle of insertion of the semimembranosus, and the area of attachment, leads to significantly different forces during landing movements. Or the femoral angle is part of a complex of features that produces more angulation on the patellar ligament in females, as well as greater genu valgum (knock knee), which in turn is associated with more adduction at the hip joint.
So you can just go to any Google site that talks about gender differences in gait, or these days, running injuries, to find out that orthopedists don't seem to agree with the idea of a similar Q angle, let alone similar knee mechanics. For instance, http://runninginjuryclinic.com/research/gender-differences-in-running-injuries/
Or here's a garden variety workout site that shows a nice set of photos
of valgus in females during loading:
But let's get more formal. Go to Index Medicus. Here's a copy and paste of abstracts of papers, mostly since 2010, that detail sex differences in the knee, and their relationship to the hips and trunk. The papers are all from recognized journals. I figured it would be more efficient to provide the actual language instead of a link. Each paragraph is a different abstract from a different paper. Some look more at biomechanical differences, some more at anatomical, some at injury risk. I've cut them down to the conclusions or in a few cases, results + conclusions, added italics and a few parentheses to foreground the bits about knees and sex differences, added a couple of definitions. The takeway, IMO, is how many ways men and women differ anatomically, and how that creates different risks of injury, in this case particularly ACL.
There were no significant sex-by-side interactions and no differences between sides. Females had greater mean anterior pelvic tilt, hip anteversion, quadriceps angles, tibiofemoral angles, and genu recurvatum than males (P<.0001). No sex differences were observed in tibial torsion (P = .131), navicular drop (P = .130), and rearfoot angle (P = .590). Sex differences in LEA (My insert: LEA = Lower Extremity Articulation) indicate that females, on average, have greater anterior pelvic tilt, thigh internal rotation, knee valgus, and genu recurvatum. These sex differences were not accompanied by differences in the lower leg, ankle, and foot. Understanding these collective sex differences in LEA may help us to better examine the influence of LEA on dynamic lower extremity function and clarify their role as a potential injury risk factor.
"Sexual dimorphism in pelvic dimensions and femoral angles of 30 males and 30 females were analyzed using landmarks on a 3D Cartesian coordinate system with geometric morphometric techniques to provide a visual representation of overall shape change in the femur and pelvis between males and females. A Principle Component Analysis (PCA) with Procrustes coordinates revealed significant shape differences in epicondylar breadth, acetabular version, and iliac flare between males and females. Analysis of the raw metric data also showed significant sexual dimorphism in the biacetabular breadth, biomechanical neck length, femoral neck-shaft angle, femoral angle of version, and the bicondylar angle."
The current results suggest that if the step width is identical, the subjects with greater knee abduction had smaller rearfoot eversion to compensate for greater hip adduction, which were more apparent in females. This explains greater knee abduction found in female runners, which can be linked to a high risk of knee injury.
The patello-femoral joint (PFJ) enhances our ability of knee flexion and extension and is assumed to have evolved through men's ability of having adopted a bipedal gait. This articulation between patella and femur is relatively complex and displays intricate biomechanical behaviour. Forces in the patello-femoral joint are a function of the quadriceps force, and the angle of flexion of the knee. They are highly dependent on the distance between the patello-femoral joint and the centre of gravity, which explains why different activities despite equivalence in tibio-femoral angle may exert wide variations in patello-femoral reaction forces and contact pressures. (My insert: This indicates that even if the femoral angle were similar, the resultant movements would not be.)
Each additional degree of internal rotation produced a reciprocal reduction of the MPFA (My insertion: Medial Proximal Femoral Angle) by 0.36degree and the AP alpha angle by 0.18degree and vice versa in external rotation.
Lower extremity alignment and Q-angles of the affected and unaffected knees were compared. RESULTS: There was a significant difference in the Q-angle between the affected (19.61+4.35) and the unaffected (17.63+4.29) side (p=0.00). (My insertion: "affected" refers to ACL injury.) There was also a significant difference in the lateral distal femoral angle (LDFA) (81.00+2.58 vs. 81.83+3.03; p=0.03)
Females landed with greater knee valgus asymmetry than males during forward landings (d=0.7, p=0.078) and with greater ankle abduction asymmetry during drop landings (d=0.5, 0.091). CONCLUSIONS: Female athletes exhibited greater frontal plane knee and ankle kinematic asymmetry than males during forward landings which may be related to the higher rate of ACL injury.
Specifically, the sex differences in potential proximal controllers of the knee as risk factors for ACL injury are identified and discussed. Sex differences in trunk and hip biomechanics have been identified in all planes of motion (sagittal, coronal and transverse). Essentially, female athletes show greater lateral trunk displacement, altered trunk and hip flexion angles, greater ranges of trunk motion, and increased hip adduction and internal rotation during sport manoeuvres, compared with their male counterparts. These differences may increase the risk of ACL injury among female athletes.
This study identified, through longitudinal analyses, that knee abduction angle was significantly increased in pubertal females during rapid adolescent growth, whereas males showed no similar change. In addition, knee abduction motion and moments were significantly greater for the subsequent year in young female athletes, after rapid adolescent growth, compared with males. The combination of longitudinal, sex, and maturational group differences indicates that early puberty seems to be a critical phase related to the divergence of increased anterior cruciate ligament injury risk factors.
In regression analysis, for the same fAP or tAP dimension, females have narrower femoral condyles or tibia platforms than males
The study found that females showed greater knee medial rotation for all the knee flexion angles (P = .02-.001), greater femoral adduction (P = .01 for all variables), with exception for 30degree (P = .13), and greater femoral lateral rotation at 60degree (P = .04). Females also showed a trend to have greater knee valgus at all the knee flexion angles (P = .06-.11) as well as less contralateral pelvis elevation at 50degree and 60degree (P = .10 and .12, respectively).
The significant difference in fascicle lengthening during eccentric contractions may be partly explained by the significantly higher patella tendon moment arm, patella tendon stiffness and Young's modulus found in males compared with females. The current study provides in vivo evidence to support the hypothesis that the tendon acts as a 'mechanical buffer' during eccentric contractions
Children had greater knee laxity than adults, whereas the dynamic tibial translation did not differ. In adults, knee laxity did not differ between the sexes, but dynamic tibial translation was greater in women. CLINICAL RELEVANCE: Children and men had less dynamic tibial translation during gait in proportion to their maximum knee laxity. The observed less dynamic tibial translation in children and adult men might be related to their reduced risk of sustaining an anterior cruciate ligament injury.
Changes in knee joint kinematics across the menstrual cycle were dependent on both the absolute and the relative magnitude of multiplanar knee laxity changes. The combination of relatively greater knee valgus coupled with relatively greater external rotation in those with large multiplanar knee laxity changes (C4) suggests an increased susceptibility to high-risk knee joint positions on ground contact and early in the landing phase. “
All female patients (both ACL-injured and uninjured) and ACL-injured male patients shared a common lateral knee geometry characterized by a smaller tibial plateau length relative to the femur and by more convex articulating surfaces of the proximal aspect of the tibia and the distal aspect of the femur. Shorter, more highly convex articulating surfaces may be inherently less stable with regard to anterior tibial translation and rotation. These findings may partially explain the greater overall predisposition of women compared with men toward ACL injury...”
OK, too much time spent on this already. Point is, there really are sex differences, they really do include a bunch of angles and biomechanical forces generated by the muscles that follow those angles, and averaged over a population, they really do create different outcomes of effort and risk. Will you find some overlap, a women with a man's knees? Well, you'll find some overlap in individual measurements, such as Q. But if you look at a basket of measurements that permit more accurate modeling of a real knee in 3D, the probability of overlap becomes miniscule, even after correction for scale. We're different, men and women. That's OK. It's not a political plot.