Gait is a highly energy efficient method of locomotion necessary for most daily activities. It involves rhythmical, reciprocal movements of the lower limbs and in terms of biomechanics reflects a destabilizing phase followed by a stabilizing phase (Magee 2006). Commonly, the gait cycle is described in terms of a stance phase (approximately 60% of time) and a swing phase (approximately 40%). The tasks involved in gait include: progression within space but also the achievement of a stable alternating one leg stand and postural stability to maintain an upright stance during all phases. Although for the majority of time gait is automatic, requiring no conscious thought, it actually comprises complex patterns of movement involving the whole body. The rhythmic, repetitive components of gait are thought to be initiated and controlled by central pattern generators within the spinal cord (S2.13). However, when changes in the internal and external environment occur, higher level centres are required to integrate and coordinate the motor response. Therefore, if the central nervous system is damaged the functional ability of a patient to walk is likely to be impaired.

The normal gait cycle is defined as the sequence of motions between two consecutive contacts of the same foot, e.g. heel strike of the left foot to heel strike of the left foot. Stance phase involves heel strike to toe off of the same lower limb (LL), while swing phase includes an initial acceleration phase through to a terminal deceleration phase. An understanding of the normal gait cycle (Figs 19.1, 19.2) and its biomechanics in terms of joint angles and muscle activity is vital to completing a sound assessment, with insufficient knowledge leading to incorrect analysis. A detailed description of normal gait is beyond the scope of this text, however a brief overview of the mechanics of the lower limb is noted below. It should be stressed that all the elements described are integrated in real-time during gait and the therapist should not forget to consider the head/neck, trunk and upper limbs, which are integral in efficient gait.