Gait is a difficult subject to understand but it regularly appears in the exam. It is therefore important to have at least a basic understanding of concepts and principles if only to make sure that you don’t end up with complete awkward salience when vivad on the topic

Step

• The length (metres) from one foot contact to the opposite foot contact 

Stride

• The length (metres) from foot contact to the same foot making contact

Cadence

• Number of steps per unit time

o    Tall people tend to have a lower cadence wshort people - higher cadence

Double support phase

• When both feet are in contact with the ground at same time
• Occurs in walking

Float phase

• When neither foot is in contact with the ground
• Occurs in running

Velocity

• Stride length divided by stride time (time for 1 gait cycle) (metres per sec)

Walking base (mm)

• Distance between the two heels when standing still

Foot Progression Angle

• Direction of foot progression from the midline
• Described as increased, positive or decreased negative

• Five prerequisites to normal walking are:

(SAFE Pre-positioning)

1. Stable stance phase

2. Adequate step distance

3. Foot clearance during swing

4. Energy conservation

5. Pre-positioning of the foot in swing phase

Gait is made smooth by the following determinants of gait:

(3 pelvic, 1 knee and 1 ankle determinant)

1. Pelvic tilt

2. Pelvic lateral displacement

3. Pelvic rotation

4. Knee flexion to allow clearance and cushioning on heel strike

5. Ankle and foot motion

Gait Cycle

Begins when foot strikes the ground and ends when same foot strikes again. From one heel strike to the next heel strike of the same leg

Therefore one cycle = 1 stride

It consists of Stance phase (60%) and Swing phase (40%)

Stance phase extends from heel strike to toe off on the same foot

Swing phase extends from toe off to heel strike on the same foot

In the stance phase, the leg is in contact with the ground and supports the body, whilst in the swing phase; it creates a new step forward.

8 sub-phases in total from heel strike to heel strike

• I Like My Tea Put In My Teapot

Stance Phase

1. Initial contact (heel strike)

2. Loading

3. Mid-stance

4. Terminal stance

5. Pre-swing (toe off)

Swing Phase

1. Initial swing

2. Mid swing

3. Terminal Swing

Stance

1. Initial contact (heel strike)

Heel contacts the ground first

Hip is flexed 30º

Knee is extended and the ankle is neutral (or slightly plantar flexed)

2. Loading response

Occupies 10-15% of gait cycle

Shock absorption is aprimary action

Ends with contralateral toe off

Knee flexes 15º while ankle plantar flexes 15º

3. Midstance

Occupies 15-20%

Body is directly over weight bearing leg

Pelvis has ceased rotating forwards

Hip and knee in full extension

Ankle is at neutral with foot in ground contact

4. Terminal stance

Occupies 20-25%

Contralateral side of pelvis rotates forwards

Hip and knee remain in extension

Foot is in neutral or plantar flexed

5. Pre-swing

Occupies 5-10%

Knee of weight bearing limb flexes and prepares for swing phase

Hip in neutral position

Knee flexion up to 35º

Ankle plantar flexed at 20º

Swing phase

1. Initial swing

Occupies 5-10%

Begins at toe off and continues until maximum knee flexion (60º) occurs

Ankle moves up 10º plantar flexion

2. Mid swing

Occupies 20-30%

Kneee extension occurs by reducing flexion of initial swing from 70º to 30º

The foot and ankle are brought up to neutral position

3. Terminal swing

Occupies 5-10%

Pelvis rotates forwards hip flexion reaches 30º, knee extends to near 0º

Ankle maintains neutral position

Figure 1. Gait cycle

 In the stance phase, the mechanics of the foot and ankle consists of 3 rockers to allow smooth gait

1st Rocker

• Very brief period between heel strike and flat foot where the landing foot prepares to receive the load
• The ankle moves from neutral to 10º plantarflexion
• The dorsiflexors (mainly tibialis anterior) contract eccentrically to control the rate of this motion
• Provide controlled plantarflexion at heel strike to prevent foot slapping
• A deceleration rocker

Figure 2. First rocker

2nd Rocker

• Between foot flat and heel off
• Allows the supporting and the rest of the body to move forwards
• Plantarflexors (gastrosoleus) eccentric contraction
• Smoothly control dorsiflexion of the ankle as body GRF moves forward
• This is also a deceleration rocker 

Figure 3. Second rocker

3rd Rocker

• Short period between flat foot and heel off
• The supporting foot prepares to take off
• Plantarflexors (Gastrosoleus) concentric contraction to provide plantarflexion
• Raises heel off floor providing toe off power
• This is an acceleration rocker
• The centre of gravity and therefore ground reaction force moves forwards with each rocker. Muscles are contracting eccentrically in the first and second rockers and concentrically in the third rocker.

Figure 4. Third rocker

Eccentric muscle contraction

An eccentric muscle contraction is in the opposite direction to the movement of the limb, i.e. the muscle lengthens as it contracts

Slows down and stabilises joint motion

·       Tibialis anterior contracts at initial contact, firing at plantar flexion as the foot is lowered to the ground

·       Gastrosoleus contracts eccentrically at mid stance

Concentric muscle contraction

A concentric muscle contraction is in the same direction as the movement of the limb i.e. the muscle shortens as it contracts.

Generates power and accelerates body forwards

·       Gastrosoleus contracts to lift the heel off the ground

·       Iliopsoas contracts flexing the hip and pulling the stance phase limb off the round

Isometric muscle contracture

An isometric muscle contraction maintains the position of the limb i.e.the muscle remains the same length as it contracts

Dorsiflexors are concentric throughout swing phase

Plantarflexors are inactive throughout swing phase

Dorsiflexors are eccentric at initial contact & loading (1st rocker)

Plantar flexors are eccentric at midstance (2nd rocker)

Plantar flexors are concentric at pre-swing (toe off) (3rd rocker)

Glutei are inactive in swing and active throughout stance

Quads are eccentric at beginning phases of stance and swing

Hamstrings eccentric throughout swing – knee flexion, and

Main differences in which the gait of small children is different are

·       Walking base is wider

·       The stride length and speed are lower and the cycle time shorter (higher cadence)

·       Small children have no heel strike; initial contact is made by flat foot.

·       There is very little stance knee flexion

·       The whole leg is externally rotated during the swing phase

·       There is an absence of reciprocal arm swinging

• There is decreased stride length, increased cycle time (decreased cadence)
• Relative increase in duration of stance phase of the gait cycle
• An increase in walking base
• Reduction in total range of hip flexion and extension, a reduction is swing phase knee flexion and reduced plantar flexion during push off.

An abnormal gait pattern may be due to

·       Muscle weakness

·       Structural deformities of the bone and/or joint

·       Neurological disorders

·       Miscellaneous

Anatalgic gait

The patient avoids weight bearing on the affected side as far as possible i.e. diminished stance phase

Denotes a painful condition of the affected side

Trendelenburg gait

The action of the abductor muscles in pulling downwards in stance phase becomes ineffective

The pelvis drops on the opposite side of the hip

Seen in polio, muscular dystrophies, perthes disease

Gluteus medius abductor lurch

The weakened abductor muscle dictates that the patient lurches towards the involved side to place the centre of gravity nearer the hip joint and reduce the moment force required to be generated by the weakened abductor muscle. This also reduces the JRF across the hip

Gluteus maximus (lurch) gait

Due to hip extensor weakness

A backward trunk lurch occurring during the stance phase to maintain the centre of mass behind the hip axi, locking the hip in extension

Quadriceps gait

The quadriceps muscle is the main extensor of the knee joint

Inability to maintain knee extension at heel strike. The patient may push on the thigh to extend the knee and lock it.