Structural Development

The beginnings of our legs and feet appear in the 3rd week of pregnancy. At this point, they are called limb buds. The limb buds grow in size and change in shape and position as the feotus develops. Here, we concentrate on the changes in position that the limb buds undergo between the 3rd and 12th week of pregnancy.

As the limb buds develop, they torsionally untwist through 180 degrees around the vertical (longditudinal) axis. Progress of this torsional untwisting is as follows:

• 6 weeks: The back of the legs and soles of the feet face the head;
• 8 weeks: The backs of the legs and soles of the feet face each other (see image opposite);
• 12 weeks: The backs of the legs and soles of the feet face away from the body (final, as born position).

As this torsional untwisting takes place, the angular relationship between the bones of the lower limbs changes. The process takes place first in the hips between the 6th and 10th week of pregnancy.

The last two bones to undergo this torsional untwisting process are the calcaneus and talus, the two bones in the rear of the foot.

The torsional untwisting of these bones takes place in the 11th and 12th week of pregnancy respectively.

By the end of the 1st Trimester (3 months) of pregnancy, the lower limbs (legs and feet) have developed and torsionally untwisted to their final (as born) position.

Torsional Untwisting of the Calcaneus (heelbone)

During the 11th week of pregnancy, the calcaneus torsionally untwists.

As this movement progresses, this bone gradually rotates about its vertical axis, bringing the rearfoot in line with the lower leg.

The ideal alignment of the calcaneus is when a line drawn through the middle of this bone is parallel with a line through the middle of the lower leg (see diagram opposite).

Torsional Untwisting of the Talus

One week later, in the 12th week of pregnancy, the Talus torsionally untwists.

The position of the talus controls the angle of the forefoot. As untwisting of the talus progresses, the forefoot rotates about its' horizontal axis so that it is parallel with the horizontal.

The ideal alignment of the talus is when the forefoot is:

a) at 90 degrees (perpendicular) to the vertical line drawn through the calcaneus (heelbone) and lower leg, and

b) parallel with the horizontal (see diagram opposite).