The mystery of the in-toeing (pigeon-toed) epidemic among young women continues:
(I am convinced that this gait is not an affectation - I am sure it is involuntary in most instances.)
The best suggested explanation came from Paul Jaminet - vitamin D deficiency; with its bone-softening effects.
This suggests that in-toeing may be a result of softening of the feet, in some way, shape or form; if not bones them perhaps joints?...
Which then leads on to the idea that it might be due to some increase in estrogen - whether natural, in contraceptives, or as an environmental pollutant (which may explain why surprising numbers of men walk this way too).
The only 'evidence' I can present for this is that estrogen softens and loosens joints (i.e. softening the ligaments that join bones to bones - this is well known in pregnancy) - perhaps making the ankles or internal joints of the foot more 'floppy', and hyper-flexible feet may cause the observed change in gait?
Well, I'm not very convinced by this - but the phenomenon is real and new, and there must be some explanation!
NOTE added - on further reflection I think the problem is likely to be neural - neuromuscular - rather than musculoskeletal - and subtly neuromuscular - hence perhaps related to basal ganglia dysfunction.
What ever causes basal ganglion dysfunction might be environmental toxins of some sort; but could also be infective - as many new diseases eventually turn-out to be.