The Gait Cycle

Original Editor - Karsten De Koster Top Contributors - Daphne Xuan and Tarina van der Stockt

The Gait Cycle

The action of walking may be summarised by the following sequence:

1. Registration and activation of the gait command within the central nervous system.
2. Transmission of gait signals to the peripheral nervous system.
4. Contraction of muscles.
5. Generation of forces across joints
6. Regulation of joint forces and moments by skeletal segments.
7. Generation of ground reaction forces.

Normal gait consists of two phases: stance phase; swing phase. These phases are further divided into a total of 8 sub-phases. The gait cycle involves a combination of open- and closed-chain activities.

Stance Phase

The stance phase occupies 60% of the total gait cycle, during which some part of the foot is in contact with the ground. It is further divided into five events:

1. Initial contact (heel strike)
2. Loading response (foot flat)
3. Mid-stance
4. Terminal stance (heel off)
5. Pre-swing (toe off)

Swing Phase

The swing phase occupies 40% of the total gait cycle , during which the foot is not in contact with the ground and the bodyweight is borne by the other leg and foot. It is further divided into 3 events:

1. Initial swing
2. Mid-swing
3. Late swing

In a complete two-step cycle both feet are in contact with the ground at the same time for 20% of the total gait cycle, 10%at the beginning of the stance phase and 10% at the end of the stance phase. These are termed 'double-support periods'. The rest of the time is spent in single support, when only one foot is in contact with the ground.

The 90-second video below gives the basics of this cycle:

Breakdown of Gait Cycle Sub-Phases

Initial Contact (or Heel Strike) - 0%

The moment the foot touches the ground and begins the first phase of double support.Its function is to establish contact with the ground surface and initiate weight acceptance.

Joint and muscle actions:

• 30° flexion of the hip, full extension in the knee, ankle moves from dorsiflexion to a neutral (supinated 5°) position then into plantarflexion.
• After this, knee flexion (5°) begins and increases, just as plantarflexion of the ankle increases.
• Plantarflexion is allowed by eccentric contraction of the tibialis anterior and dorsiflexors.
• Knee flexion is allowed by a concentric contraction of the knee flexors and eccentric contraction of the knee extensors.
• Flexion of the hip is caused by the contraction of the rectus femoris.

	Kinematics	Muscle Action
Ankle	Neutral, 0°	Concentric to eccentric dorsiflexors
Knee	5° flexion	Eccentric extensors
Hip	30° flexion	Concentric extensors

Loading Response (or Foot Flat) - 0-10%

Begins with initial contact and continues until the contralateral foot leaves the ground. The foot continues to accept weight and absorb shock by rolling into pronation.

Joint and muscle actions:

• Hip moves slowly into extension, caused by a contraction of the adductor magnus and gluteus maximus muscles.
• Knee flexes to 15° to 20° of flexion.
• Ankle plantarflexion increases to 10-15°.

	Kinematics	Muscle Action
Ankle	Rapid plantarflexion to 10°	Eccentric dorsiflexors
Knee	Flexes to 10-15°	Eccentric extensors
Hip	Gradual extension	Concentric extensors

Midstance - 10-30%

Begins when the contralateral foot leaves the ground and continues until ipsilateral heel lifts off the ground. The body is supported by a single leg and begins to move from force absorption at impact to force propulsion forward.

Joint and muscle actions:

• Hip moves from 10° of flexion to extension by contraction of the hip extensors.
• Knee reaches maximal flexion and then begins to extend.
• Ankle becomes supinated and dorsiflexed (5°), which is caused by some contraction of the triceps surae muscles.

	Kinematics	Muscle Action
Ankle	Gradual dorsiflexion	Eccentric plantarflexors
Knee	Begins to extend	Concentric extensors
Hip	Gradual extension	Concentric extensors

Terminal Stance (or Heel Off) - 30-50%

Begins when the heel leaves the floor and continues until the contralateral foot contacts the ground. In addition to single limb support and stability, this event serves to propel the body forward.

Joint and muscle actions:

• Bodyweight is divided over the metatarsal heads.
• 10-13° of hip hyperextension, which then goes into flexion.
• Knee becomes flexed (0-5°)
• Ankle supinates and plantar flexes.

	Kinematics	Muscle Action
Ankle	Gradual dorsiflexion until a maximum of 10° before beginning to plantarflex	Eccentric plantarflexors then concentric plantarflexors
Knee	Continues extending until a maximum of 5° of flexion before beginning to flex	Concentric extensors then Eccentric extensors
Hip	Extends until a maximum of 10° extension	Eccentric flexors

Pre-Swing (or Toe Off) - 50-60%

Begins when the contralateral foot contacts the ground and continues until the ipsilateral foot leaves the ground. Provides the final burst of propulsion as the toes leave the ground.

Joint and muscle actions:

• Hip becomes less extended.
• Knee is flexes to 35-40°
• Plantarflexion of the ankle increases to 20°.

	Kinematics	Muscle Action
Ankle	Begins to plantarflex rapidly before foot leaves the ground	Concentric plantarflexors
Knee	Begins to flex rapidly	Eccentric extensors
Hip	Begins to flex before foot leaves the ground	Eccentric flexors then concentric flexors

Early Swing - 60-75%

Begins when the foot leaves the ground until it is aligned with the contralateral ankle. This event functions to advance the limb and shorten the limb for foot clearance.

Joint and muscle actions:

• Hip extends to 10° and then flexes due to contraction of the iliopsoas muscle 20° with lateral rotation.
• Knee flexes to 40-60°
• Ankle goes from 20° of plantar flexion to dorsiflexion, to end in a neutral position.

	Kinematics	Muscle Action
Ankle	Continues to plantarflex until a maximum of 20° before moving back towards a neutral position	Eccentric dorsiflexors then concentric dorsiflexors and eccentric plantarflexors
Knee	Rapid knee flexion	Eccentric extensors and concentric flexors
Hip	Gradually flexes	Concentric flexors

Mid-Swing - 75-85%

Begins from the ankle and foot alignment and continues until the swing leg tibia is vertical. As in early swing, it functions to advance the limb and shorten the limb for foot clearance.

Joint and muscle actions:

• Hip flexes to 30° (by contraction of the adductors) and the ankle becomes dorsiflexed due to a contraction of the tibialis anterior muscle.
• Knee flexes 60° but then extends approximately 30° due to the contraction of the sartorius muscle(caused by the quadriceps muscles).
• Ankle remains neutral.

	Kinematics	Muscle Action
Ankle	Maintains a neutral position	Concentric dorsiflexors
Knee	Reaches a maximum of around 60° flexion	Eccentric extensors and concentric flexors
Hip	Continues to flex until a maximum of just over 30°	Concentric flexors

Late Swing/Deceleration - 85-100%

Begins when the swing leg tibia is vertical and ends with initial contact. Limb advancement slows in preparation.

Joint and muscle actions:

• Hip remains flexed to 25-30°.
• Locked extension of the knee.
• Ankle remains neutral.

	Kinematics	Muscle Action
Ankle	Maintains a neutral position	Concentric dorsiflexors
Knee	Extends until full extension, and flexes just slightly before initial contact	Eccentric flexors, then concentric flexors
Hip	Hip remains flexed to around 30 °	Concentric flexors

Clinical Application

Understanding the gait cycle allows for effective gait analysis. When analysing gait, it should be done systematically, looking at each joint separately throughout the entire gait cycle and detecting deviations from normal. Injury or disease can alter any of the sub-phases of the gait cycle, resulting in distinct characteristics of the gait pattern.