The study of human motion reveals a greater understanding of the dynamics of the different joints and muscles of the body and how these interlink to provide for the efficient movement of the lower limbs.
The gait cycle comprises of two phases: stance and swing. The stance phase occurs when the foot is in contact with the ground whereas the swing phase refers to the portion of the gait cycle when the foot is in the air.
While a single stance represents 60% of the normal gait cycle, the swing phase accounts for the remaining 40%. Variations could prevail in this percentage as gait velocity increases or decreases.
A stride is counted as one complete gait cycle, that is, from heel strike to the next heel strike of the same foot.
A normal gait is marked by the following characteristics - the leg is able to support body weight without collapsing, balance is maintained during the single support phase, there is an advance in swing leg to take over and there is sufficient power for necessary limb movements.
This would enable the foot to hit the ground in enough supination to create a time delay in functional pronation, to resupinate by midstance in order to have a propulsive lever, to propel the medial side of the forefoot and to prevent functional hallux limitus.
The ankle/foot dynamics play an important role during gait in terms of absorbing shock and aiding progression of the body’s centre of mass. This becomes more evident during the swing phase.
Ankle dorsiflexors undergo brief eccentric contraction in pre-swing, followed shortly by concentric contraction at the initiation of swing.
Most of the knee motion is limited to the sagittal plane. Like the ankle/foot muscles, the role of these muscles is more prevalent as the limb is in swing, with passive knee flexion in early swing phase.
During swing, the knee passively extends as a result of the change in the hip joint from flexion to extension. Mid-to-late swing sees all three hamstrings decelerate the extending knee to prevent excess knee flexion.
Hip flexion is important as it marks the transition from stance to swing, advancing the trailing limb and assisting in foot clearance through concentric contractions of the iliopsoas, rectus femoris, and sartorius muscles.
Any deviations in the normal pattern of gait induces altered joint motion.
This can, in turn, lead to hypermobility which produces joint subluxations.
A thorough gait assessment helps identify not only the postural abnormality but also the source from where it originates. This enables us to gain as much information about the pathology as possible and to accordingly recommend suitable forms of treatment.
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