Sagittal plane pivots or rockers:
The body creates power from above for forward progression the foot must allow this forward progression, the foot must presumable act as a pivot in the sagittal plane.
The three sites of rotation or sagittal plane pivots are:
1) Plantar surface of calcaneus (heel rocker/first rocker) – rounded plantar surface of calcaneus is the initial pivotal site by permitting the foot to move to the ‘foot flat’ position allows the foot to plantarflex at heel contact – this pivot allows no more motion once the forefoot contacts the ground next pivot/rocker is used
2) Ankle (ankle rocker/second rocker) – this pivot permits the body to move over the foot – normally there is considered to be 10 degrees of motion of the leg past vertical as heel begins to unweight
3) Metatarsophalangeal joints (forefoot rocker/third rocker)– as the heel unweights, the MPJ’s become the next pivot in the sagittal plane – allows acceleration of forward progression with heel off
Abnormalities in any of these pivots or rockers are assumed to impede forward progression and lead to compensatory changes in other structures.