Gait Cycle

The gait cycle is the time interval between any of the repetitive events of walking, such an event could include the point when the foot first contacts the ground to the point when the same foot contacts the ground again.

Gait Cycle begins when the foot strikes the ground and ends when the same foot strikes the ground again.

Learning and understanding the gait cycle is very important in evaluating lower limb problems, as much can be learnt by carefully studying the way the patient walks and moves. It is not clear whether gait is learned or is preprogrammed at the spinal cord level.

A single gait cycle consists of a stance phase (60%) and a swing phase (40%).

See Also: Foot Anatomy

Definitions

Stride length: it’s one full gait cycle from heel strike to another heel strike. It’s measured from initial contact at the start of stance to the next initial contact of the same foot. Each stride is composed of a stance phase and a swing phase.
The average stride length for normal adults is 144 m (56 in.).

Step Width: The step width is the distance between both feet. The normal step width, which is considered to be between 5 and 10 cm (2–4 in.).

Step Length: Step length is measured as the distance between the point of initial contact of one foot and the point of initial contact of the opposite foot. The average step length is about 72 cm (28 in.). The measurement should be equal for both legs.
Two step lengths added together make the stride length.

Walking: it’s a period of double limb support in addition to always having one foot in contact with the ground throughout the gait cycle.

Stance Phase: it’s the period of time when the foot is on the ground, in which the leg accepts body weight and provides single limb support. It’s 60% of one gait cycle.

Swing phase: it’s the period of time that the foot is off the ground, in which the limb advances forward.

Velocity: defines steps per unit of time.

Ground reaction forces (GRF): it is the force exerted by the ground on a body in contact with it. GFR is approximately 1.5 times body weight during walking and 3 to 4 times body weight during running.

There are two peaks of ground reaction force during the gait cycle:

1. the first at maximum limb loading during the loading response,
2. the second during terminal stance.

The ground reaction force vector changes from anterior to the hip joint at initial contact to a progressively posterior position at late stance, when the ground reaction force is posterior to the hip.

Newton’s third law states that for every action there is an equal and opposite reaction.

Typically, the step and stride lengths do not vary more than a few centimeters between tall and short individuals. Men typically have longer step and stride lengths than women.

Step and stride lengths decrease with age, pain, disease, and fatigue.

A decrease in step or stride length may also result from a forward head posture, a stiff hip, or a decrease in the availability of motion at the lumbar spine.

The decrease in step and stride length that occurs with aging is thought to be the result of a number of factors including an overall decrease in joint range of motion, and the increased likelihood of falling during the swing phase of ambulation, caused by diminished control of the hip musculature. This lack of control prevents the aged person from being able to intermittently lose and recover the same amount of balance that the younger adult can lose and recover.

Gait Cycle Phases

Normal gait cycle phases are divided into stance and swing phases.

Stance Phase

Stance Phase constitutes approximately 60–65% of the gait cycle, and describes the entire time the foot is in contact with the ground and the limb is bearing weight.

The stance phase begins when the foot makes contact with the ground and concludes when the ipsilateral foot leaves the ground.

The stance phase takes about 0.6 seconds during an average walking speed.

Heel Strike:

Heel Strike is defined as the initial contact of the foot heel on the ground.

Muscles actions:

• Hip extensors contract to stabilize the hip.
• Quadriceps and tibialis anterior muscles contract eccentrically: this Controls the rate at which foot strikes the ground.

Hindfoot is locked/inverted at initial strike allows for energy absorption

Foot flat:

Gastrocnemius-soleus complex eccentrically contracted during flat foot position: this controls forward progression of body over the foot.

Hindfoot is unlocked/ everted for ground accommodation.

Mid-stance:

• From elevation of opposite limb until both ankles are aligned in coronal plane.
• Hip extensors and Quadriceps muscles has a concentric contraction.

Terminal stance

• Begins when the supporting heel is of the ground, and continues until the opposite heel touches the ground.
• Toe flexors and tibialis posterior muscles contract (the most active muscles during this phase).

Preswing Stance:

The preswing interval begins with initial contact of the contralateral limb and ends with the ipsilateral toe-off.

During this phase, the stance leg is unloading the body weight to the contralateral limb and preparing the leg for the swing phase.

Swing Phase

Swing phase is 40% of the cycle. Gravity and momentum are the primary sources of motion for the swing phase. Within the swing phase, one task and three intervals are recognized.

Toe-off:

• Defined as the time from elevation of limb (toes are off the ground) to maximal knee flexion.
• Gastrocnemius-soleus complex has a concentric contraction.
• Hindfoot supinates, with activating the posterior tibialis tendon.
• Transverse tarsal joint locks and provides a rigid lever arm for toe-off.
• It represents the 60–73% phase of the gait cycle.

Mid-swing:

• Defined as the time from maximal knee flexion to where the tibia is vertical to the ground.
• Ankle dorsiflexor muscles contract to ensure foot clearance.
• It represents the 73–87% phase of the gait cycle.

Terminal swing:

• Defined as the time from where the tibia is vertical to just prior to another initial contact (heel strike).
• Hamstring muscles decelerate forward motion of the thigh.
• It represents the last 87–100% of the gait cycle.

Center of gravity (COG)

The trunk center of gravity of body mass is located just anterior to T10, which is 33 cm above the hip joints in an individual of average height (184 cm).

The body’s line of gravity is anterior to S2 and provides a reference for the moment arm to the center of joint under consideration. the resulting gait pattern resembles a sinusoidal curve.

Important characteristics of gait cycle

Normal gait cycle requires stance-phase stability, swing-phase ground clearance, correct position of the foot before initial contact, and energy-efficient step length and speed.

Throughout stance phase, 12% of time is spent in double-limb support. 38% of stance spent in single-limb support.

During normal walking, the body’s center of gravity is subject to both vertical and lateral displacement. Minimizing trunk displacement optimizes energy expenditure during bipedal gait.

In the sagittal plane of the body, vertical displacement follows a sinusoidal curve with amplitude of 5 cm.

Lateral displacement also follows a sinusoidal curve, with an amplitude of 6 cm.

Determinants of Gait

There are six determinants of gaits that work in concert to minimize vertical and lateral displacement during normal walking. These six determinants also represent the six degrees of freedom of gait and are defined by the flexion and extension of each of the three joints involved in gait (hip, knee, ankle).

Pelvic rotation: During forward motion, the pelvis externally rotates from initial contact to onset of preswing, and internally during preswing and swing. This symmetric net rotation minimizes the total vertical plane displacement needed for limb retraction and advancement in swing and stance.

Pelvic list (tilt): non–weight-bearing contralateral side drops 5 degrees, reducing superior deviation.

Knee flexion at loading: stance-phase limb is flexed 15 degrees to dampen the impact of initial loading.

Foot and ankle motion: through subtalar joint, damping of loading response occurs, leading to stability during
midstance and efficiency of propulsion at push-off.

Knee motion: knee works together with foot and ankle to decrease necessary limb motion. The knee flexes at initial contact and extends at midstance.

Lateral pelvic displacement: relates to transfer of body weight onto limb. Length of motion is 5 cm over the weight-bearing limb, narrowing the base of support and increasing stance-phase stability.

Gait Cycle Muscles

• Agonist and antagonist muscle groups work in concert during the gait cycle to effectively advance the limb through space.
• Hip flexors advance the limb forward during swing phase and are opposed during terminal swing, before initial contact by the decelerating action of the hip extensors.
• Most muscle activity is eccentric, which is muscle lengthening (aka elongation) while it contracts and allows an antagonist muscle to dampen the activity of an agonist  and act as a “shock absorber”.
• Isocentric contraction is muscle length’s remaining constant during contraction.
• Some muscle activity can be concentric, in which the muscle shortens to move a joint through space.
• Tibialis anterior has both eccentric (heel strike) and concentric (swing) muscle actions during normal gait.

Muscle	Action	Function
Gluteus medius	Eccentric	Controls pelvic tilt (midstance)
Gluteus maximus	Concentric	Powers hip extension
Iliopsoas	Concentric	Powers hip flexion
Hip adductors	Eccentric	Control lateral sway (late stance)
Hip abductors	Eccentric	Control pelvic tilt (midstance)
Quadriceps	Eccentric	Stabilizes knee at heel strike
Hamstrings	Eccentric	Control rate of knee extension (stance)
Tibialis anterior	Concentric	Dorsiflexes ankle at swing. Slows plantar flexion rate during heel strike
Gastrocnemius soleus	Eccentric	Slows dorsiflexion rate (stance)

Abnormal Gait patterns

Factors that lead to abnormal gait include muscle weakness, neurologic conditions, pain, limb deformity, and joint disease.

Muscle weakness or paralysis: decreases ability to normally move a joint through space. Walking strategies develop on the basis of the specific muscle or muscle groups involved and the ability of the individual to acquire a substitution pattern to replace that muscle’s action.

Neurologic conditions: may alter gait by producing muscle weakness, loss of balance, reduced coordination between agonist and antagonist muscle groups (ispasticity), and joint contracture.

• Hip scissoring is associated with overactive adductors, and knee flexion may be caused by hamstring spasticity.
• Equinus deformity of the foot and ankle may result in steppage gait and backwards setting of the knee.

Pain in a limb: creates an antalgic gait pattern in which the individual shortens stance phase to lessen the time the painful limb is loaded. The contralateral swing phase is more rapid.

Joint abnormalities: alter gait by changing the range of motion of that joint or producing pain.

• A hip and knee with arthritis may have joint contractures and reduced range of motion.
• An anterior cruciate–deficient knee has quadricepsavoidance gait, which represents a decreased quadriceps moment during midstance.

Antalgic gait

• A markedly shortened stance phase on one side.
• Pain makes the patient move off the affected limb as quickly as possible.
• The step length may be short

Scissoring gait

• A stiff-legged gait with the legs crossing each other is often associated with the muscle imbalance found in cerebral palsy.
• Often, there is also a crouched posture with flexed hips and knees, feet that are in equinus and both limbs internally rotated.

Drop-foot gait

During swing phase, there is no ‘pick up’ of the foot so it effectively ‘drops’ into equinus; if the foot was not lifted higher than usual to accommodate this, the toes would drag along the floor.

This is caused by disorder or damage to the peripheral nerves supplying the foot dorsiflexors (peroneal nerve)

High-stepping gait

This could be due to a bilateral foot drop or it may signify problems with balance or proprioception.

Waddling gait (Trendelenburg gait)

• The trunk is thrown from side to side with each step.
• The mechanics are similar to those that produce a positive Trendelenburg test as seen in patients with functionally weak abductor muscles of the hip, perhaps due to dislocation or simply pain.

See Also: Trendelenburg Test

Ataxic gait

Ataxia produces a more obvious and irregular loss of balance, which is compensated for by a road-based gait, or sometimes uncontrollable staggering.

Dystonia

Dystonia refers to abnormal posturing (focal or generalized) that may affect any part of the body and is often aggravated when the patient is concentrating on a particular motor task such as walking.

Common problems in Gait noticed by parents

Toe-Walking

Tiptoe walking or toe-walking is often a common complaint. In fact, many children, while learning to walk, tend to walk on their toes. Painless toewalking, especially if it is on both sides, is benign and often labeled as idiopathic. However, every child examined must be carefully evaluated to rule out conditions like mild spastic diplegic cerebral palsy and hereditary spastic paraparesis, tendon achilles contracture, etc. If toe-walking is present on one side, then shortening of the lower limb might be a possibility.

In-Toeing Gait

Parents often bring their child saying, “He/she walks abnormally with feet falling in reverse direction or the feet cross each other while he/she walks.” When a child walks with the foot progression angle values in negative, i.e., when the feet are directed toward each other instead of being directed away from each other, the gait pattern is said to be in-toe. In most children, it is harmless and tends to improve with age, especially if it is bilateral, symmetrical, and painless due to increased femoral anteversion. The child should also be examined to rule out other causes of torsional anomalies of the lower limb, like intorsion of the tibia, torsional malunion (unilateral), and metatarsus adductus deformity, among other possible causes.

Out-Toeing Gait

This is an uncommon cause of hospital visit compared to in-toeing, and the usual gait pattern is of out-toeing. The usual amount of out-toeing recorded is between 0° and 30°, and this tends to improve with age. The persistence of out-toeing is suggestive of torsional anomalies of the tibia.

Crutches and canes

Crutches and canes are devices that ameliorate instability and pain, respectively.

Crutches increase stability by providing two additional load points.

A cane helps shift the center of gravity to the affected side when the cane is used in the opposite hand. This decreases the joint reaction of the lower limb and reduces the pain

References

• Mann RA, Hagy J. Biomechanics of walking, running, and sprinting. Am J Sports Med. 1980 Sep-Oct;8(5):345-50. doi: 10.1177/036354658000800510. PMID: 7416353.
• Gait Analysis: Normal and Pathological Function. J Sports Sci Med. 2010 Jun 1;9(2):353. PMCID: PMC3761742.
• Perry J: Stride analysis. In: Perry J, ed. Gait Analysis: Normal and Pathological Function. Thorofare, NJ: Slack Inc, 1992:431–441.
• Donatelli R, Wilkes R: Lower kinetic chain and human gait. J Back Musculoskelet Rehabil 2:1–11, 1992.
• Levine D, Whittle M: Gait Analysis: The Lower Extremities. La Crosse, WI: Orthopaedic Section, APTA, Inc., 1992.
• Mann RA, Hagy J: Biomechanics of walking, running, and sprinting. Am J Sports Med 8:345–350, 1980.
• Mann RA, Hagy JL, White V, et al: The initiation of gait. J Bone Joint Surg Am 61A:232–239, 1979.
• Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.
• Millers Review of Orthopaedics -7th Edition Book.