Gait CoM, Determinates of gait, abnormal gaits

Question 1

What is the Centre of Mass? (CoM)

Answer 1

The point at which the external force of gravity will act.
The Centre of Mass lies slightly anterior to S2 in most people.

Question 2

What is being assessed in a CoM during the gait?

Answer 2

Vertical displacement (inverted pendulum) The highest point of VD is in midstance and the lowest = Heel strike.

Lateral Displacement. ( hips oscillates laterally towards the supporting leg)

Question 3

What are the 6 determinants of gait? And how is it linked to CoM?

Answer 3

1. Pelvic rotation
2. Pelvic tilt
3. Knee flexion
4. Foot mechanisms
5. Ankle mechanisms
6. Lateral displacement of the body.

This method It allows for a smooth and efficient walking gait by minimising large fluctuations in the CoM.

Question 4

1. Pelvic rotation (determinants of gait)

Answer 4

Anterior rotation of the pelvis in the transverse plane
4° either side during swing phase.
Reduces the angle of hip flexion/ extension.
Enables a longer step length
reduces CoM displacement

Question 5

2. pelvis tilt (determinants of gait)

Answer 5

During hip swing phase
reduces the height of CoM
Presents of ‘dip’ during standing on unsupported leg. (classic Trendelenburg sign)

Question 6

3. Knee flexion during stance stance phase

Answer 6

15° flexion during stance phase
‘shortens’ the leg during stance phase
This will reduce the height of the CoM during the stance phase.

Question 7

4. Ankle Mechanism

Answer 7

Lengthens the leg at initial contact
Reduces the need for excessive hip tilt
Reducing the lowering of CoM during initial contact
Smoothen the CoM curve

Question 8

5. Foot mechanism

Answer 8

Increases the length of the leg as the heel raises off the ground in terminal stance
This minimises the rise and fall of the hip ( if this foot mechanism wasn’t present the hip and knee would need to be under more flexion, this will cause a shift in the CoM than simply raising a heel.
Thus the foot mechanism avoids excessive hip and knee flexion.

Question 9

6. Lateral displacement of the body.

Answer 9

CoM must shift over towards the stance foot to provide balance
This is facilitated by a small walking base (8cm)
Valgus angulation at the knee allows this shift in the centre of mass during walking with very little effort.

Question 10

What does the 6 detrimental gait allow?

Answer 10

It allows for a smooth and efficient walking gait by minimising large fluctuation in the CoM.

Question 11

Abnormal Gait

Answer 11

Antalgic gait: Gait that occurs as a result of pain manifestation. i.e Pt avoids placing weight on the effective side.
This will result in a decreased stance phase, decreased step length, Decrease stride length

Ataxic Gait: Occurs as a result of a loss of muscle movement. Wide base, staggered line of progression, the appearance of stumbling/ drunkenness. Conditions such as stroke, cerebral palsy, MS.

Hemiplegic Gait: Unusual. Unilateral weakness in effect side. Abnormal arm swing, Leg circumduction. Usually, the legs are constantly in contraction. Common in stroke and spinal cord injury.

Diplegic Gait: Similar to hemiplegic but on both sides.
Lower limb is affected more e than the upper limb.
Both legs dragged along the ground.
Common on cerebral palsy and extreme tightness of hip adductors. Cause legs to cross the midline.

Neuropathic Gait: High stepping gait.
Foot drop due to loss of dorsiflexion,
Toes drag while walking.
Pt unable to walk on their heels.
Pts overcompensate for this by excessive knee and hip flexion.

Sensory Gait: Loss of proprioceptive input,
Feet hit the floor with a high velocity.
Pt can not feel when they have hit the floor.
Occurs in diseases affecting peripheral nerves, spinal cord injury, exposure to toxins.

Trendelenburg gait: A lateral shift of the trunk ipsilateral to the step.
e.g. Right step=left hip drop and body leans right.

Myopathic Gait: Waddling gait, bilateral Trendelenburg signs