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21 GAIT ANALYSIS
D Casey Kerrigan, MD
Ugo Della Croce, PhDINTRODUCTION
- Gait, referring to humans walking and running, is one
of the most obvious and fundamental actions in life. - Recognizing and describing gait patterns is just the
first step toward appreciating the complexity of gait
physiology. When trying to improve upon a person’s
gait pattern, the complexity of gait becomes evident.- The ultimate goal of gait analysis is to understand the
complex relationships between an individual’s capa-
bilities/impairments and the person’s gait pattern, so
as to enhance performance while preventing injury
(Birrer et al, 2001). - Gait analysis is also used to understand the effects of
external biomechanical factors such as shoes or
orthoses.
GAIT CYCLE- The basic unit of walking and running is the gait
cycle, orstride. Perry and colleagues described var-
ious temporal and functional variables within the
gait cycle (Kerrigan and Edelstein, 2001), which
have become a standard reference to describe gait
(Fig. 21-1). - Walking gait cycle timing is primarily divided into
double supportand single supportphases. - When focusing on each leg’s activity, the cycle is
divided into the stance and swingperiods which
begin at initial and final contact of the foot, respec-
tively. - When focusing on functional aspects of gait, the
walking gait cycle can be divided into three functional
tasks: weight acceptance, single limb support and
limb advancement; the first two occurring during
stance and the third occurring primarily during swing.
The tasks are further subdivided into eight phases:
weight acceptance comprises initial contactand load-
ing response, single limb support comprises mid-
stance, terminal stance and preswing, and limb
advancement comprises initial swing,mid-swing, and
terminal swing. - Temporal-spatial gait parameters consist of the fol-
lowing: Stride time refers to the time from initial con-
tact of one foot to initial contact of the same foot, step
timerefers to the time from initial contact of one foot
to initial contact of the opposite foot, stride lengthand
step lengthrefer to the distances traversed during the
respective times. Gait velocity is the ratio between
stride length and stride time. Cadence of gait refers to
the stride (or step) frequency, i.e., the number of
strides (or steps) per unit of time.
•Temporal-spatial parameters can be effectively meas-
ured during either walking or running with pressure
mats (cellular mats measuring foot pressure), force plat-
forms (dynamometers sensing ground reaction forces in
time), and motion analysis (system of stereophotogram-
metric cameras for 3D reconstruction of body motion,
126 SECTION 2 • EVALUATION OF THE INJURED ATHLETE