A normal walking gait pattern depends on some key biomechanical features that are known as the determinants of gait. These six determinants of gait were introduced by Saunders in 1953, and have been widely embraced with some modifications and minor issues. The determinants of gait are considered important as they ensure a more economical locomotion by the reducing the vertical centre of mass movement that leads to a reduction in the metabolic energy needed for movement. The principle underpinning this is that a better control of these determinants of gait leads to an increase in energy conservation and more efficient movement. The theory that does underpin these determinants of gait are in conflict with the ‘inverted pendulum’ theory which views the static stance leg acts as a pendulum that follows an arc. The biomechanics community continues to debate the merit of the two approaches.
The six determinants of gaits and how they affect the centre of mass (COM) displacement and energy conservation are:
1. Pelvic rotation: The pelvis rotates side to side during normal gait to aid in the progression of the contralateral side through reduced hip flexion and extension. This affects the reduction of metabolic energy and the increased energy conservation by reducing the vertical COM displacement.
2. Pelvic tilt: During normal gait there is a tilting of the swing phase side of the pelvis that is controlled by the hip abductor muscles. This muscle action reduces the raising of COM during the transition from hip flexion to extension. This will reduce the use of metabolic energy and increase energy conservation by reducing vertical COM movement.
3. Knee flexion during stance phase: The knee is extended at heel strike and then begins to flex when foot is on the ground. This knee flexion will lower the apex of the vertical trajectory of the COM resulting in some energy conservation.
4. Motion at the foot and ankle: The ankle rockers at heel strike and mid-stance leads to decrease COM displacement through the shortening of the leg play a role by reducing the COM vertical displacement.
5. Knee motion: The motion of the knee is related to those of the ankle and foot motions and results in the reduction of COM vertical displacement and leads to decreases in the COM displacement and energy cost.
6. Lateral displacement of the body: the lateral movement of the pelvis or a relative adduction of the hip is mediated by the effect of tibiofemoral angle and relative adduction of the hip to reduce vertical COM displacement. It is considered that this feature plays a critical role in ensuring efficiency in normal gait.
These six determinants of gait are logically appealing as they help us focus on some key factors to keep the COM movement smooth and improve the efficiency of gait. However, some recent research questions whether all or some of the determinants are really that important in the overall scheme of the events that happen during the gait cycle. Despite that considering these determinants is fundamental in understanding gait disability.