Heel struts

Heels this high can really turn heads!

And who designs a robot with high heels?

I don't know, but when I find him, aarugh!Sari Sumdac and Flareup, "Bee in the City"

"Heel struts" (also sometimes referred to as High Heels) are part of Transformer anatomy. They are common on Transformers who have a relatively low foot surface area whose point-of-contact is concentrated somewhere forward of the ankle joint.

This arrangement allows a Transformer greater dynamic stability by re-locating the ankle joints away from the center-of-balance axis, and reduces wear on the ankles by allowing the foot to flex before absorbing an impact. Heel struts can increase the leverage afforded by the ankle joints by distributing the pressure over a larger area, dramatically increasing a Transformer's static stability without the need for big, clunky feet.

Heel struts are more common on Transformers with small frames or a high center of gravity. It has been noted that a disproportionate number of female Transformers have heel struts... but female Transformers also tend to have smaller frames and lack the big clunky feet of many male Transformers. Of course, some male characters have heel struts, so maybe that balances it out.

Also, they make their butts move sexily when they walk.

Heel struts should not be confused with reverse articulated knees or triple-jointed legs, both of which feature the forward-canted foot, but typically lack the stabilizing strut behind it.

Fiction

Prime cartoon

When the Autobots were trying to figure out how MECH built Nemesis Prime, Ratchet said that MECH disassembled Breakdown "from cranial chamber to heel-strut". Nemesis Prime

Smokescreen once called Starscream 'the stiletto-heeled freak'.