How the foot moves
Movements occur in the joints. The most important joint is the ankle between the shin and the talus. The directions of movement are moving the foot upwards (dorsiflexion), moving the toes downwards (plantar flexion), turning the sole inwards (supination) and turning the sole outwards (pronation). Different groups of muscles work together to move the foot.
1. Heel strike to foot flat (supination)
When the heel touches the ground, the foot is slightly supinated and followed by strong pronation. This is easiest to see during running. The ankle is loose and open.
2. Foot flat to midstance
When the sole touches the ground, it remains loose to neutralise the forces and adapt to the surface of the ground.
3. Midstance to heel off
Before lifting the heel the joint is straightened and the foot supinates from its neutral position.
4. Heel off to toe off
Toe off means lifting the body. The foot is supinated and the joint is in a locked position.
The weight line
The areas where the most pressure exerted during walking form a line, which is called the weight line. The weight line of a healthy foot is S-shaped, starting from the inside heel, then turning inwards and splitting in two in the middle of the metatarsals going towards the big and little toes. A healthy foot has a normal weight line, while the weight line of problem feet has a characteristic pattern which differs from this.