Gait

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Information about Gait
Health & Medicine

Published on March 8, 2014

Author: DrPRANEETHREDDY

Source: slideshare.net

Description

HUMAN GAIT

  By Dr C.V.Praneeth Reddy Final YR PG ASRAM ELURU

The gait may be defined as the forward propulsion of body by the lower limbs in a systematic,coordinated semirotatory movements of the trunk,arm and head. An interplay between loss and recovery of balance with constant change in the centre of gravity,causing the forward propulsion of an organism from one place to another.

    Human locomotion is a complex task. Because of inherent differences in anatomical structure, motor control patterns, and pathological or chronological changes, each person's gait pattern is unique. However, because everyone has the same basic anatomic and physiological makeup, human locomotion occurs in a similar manner for everyone. The cyclical and highly automated movement pattern during human locomotion involves rhythmic, alternating motions of the trunk and extremities.

 There is a clear link between human gait characteristics and different medical conditions.  For e.g. high stepping gait in foot drop, trendelenberg gait in unstable gait. hand to knee gait in quadriceps weakness.

 Factors required for normal synchronous walking pattern  Adequate base of support. Appropriate foot clearance during swing. Adequate step length. Conservation of energy.   

 It is the time interval or sequence of motions occuring between two consecutive initial contacts of the same foot.  If heel strike is the initial contact,the gait cycle is from one heel strike to the next heel strike on the same foot.

 Base of support : is the distance between a person’s feet while standing and during ambulation.  It provides both support and stability to maintain an erect posture.  Normally it should not be more than 2-4 inches from heel to heel.

 Step length : the linear distance measured along the line of progression representing how one foot has travelled during one Gait cycle.  The average length of a step is approximately 15 inches.

    Stride length : it is the linear distance in the plane of progression between two consecutive point of foot to floor contact of the same foot. Normal : 27-32 inches Cadence : number of steps taken per minute. Normal : 90-120 steps for adult.

   Double limb support : Consists of that portion of the gait cycle when both feet,the heel of the foot and the toe of the other are simultaneously in contact with the ground. During the period of double support,the centre of gravity is at its lowest point.

     Centre of gravity : It is an imaginary point at which all the weight of the body is concentrated at a given instant. Lies two inches in front of the second sacral vertebra. Follows an up and down movement as well as the side to side movement. Follows a smooth sinusoidal curve and oscillates no more than 2 inches up and down and from side to side.

   Knee flexion in stance phase The knee should remain flexed during all components of stance phase(except heel strike) to prevent the excessive vertical displacement of the centre of gravity. For example,in toe off when the ankle with 20 deg. of plantar flexion,tends to cause the centre of gravity to rise,the knee flexes to approximately 40 deg. to counterbalance it.

    Pelvic rotation : During normal gait,the normal pelvis rotates 8 deg. within the transverse plane of the body. This 8 deg. is broken down as 4 deg. forward on the swing leg and 4 deg. posteriorly on the stance leg. Pelvic rotation lengthens the femur during the swing phase through initial foot contact and helps to minimize the vertical trunk displacement during gait to conserve energy.

    Pelvic tilt : The pelvis also rotates within the frontal plane of the body during gait,which is termed as “pelvic tilt”. This creates a downward motion of the pelvis of approximately 5 deg. on the weight bearing limb during stance. The “listing” of the pelvis creates adduction of the weight bearing limb and abduction of the non-weight bearing limb,thereby improving the efficacy of the hip abductor mechanism.

 The pelvis and the trunk shift laterally approximately one inch to the weight bearing side during gait to centre the weight over the hip.

    Foot and ankle motion : Ankle is dorsiflexed at heel strike and plantar flexed at toe off. The dorsiflexors contract eccentrically from initial heel contact with the ground,to keep the foot from slapping to the floor. The foot acts as a shock absorber by pronating during the stance phase,during toe-off the foot serves as rigid lever.

  The trunk,shoulders,arms also rotate to ensure balance and stability during gait. The upper limb swings in tandem with the opposite stance leg in the lower extremity to produce as smooth balanced gait.

   Two phases Stance phase – when the foot is off the ground. Swing phase – when limb is moving forward.

    Begins when the foot contacts the ground and ends when the foot lift off the ground. Constitutes 60% of gait cycle. Most problems become apparent during stance phase because it bears weight and undergoes greater stress. Stance phase is divided in to the following components-

     Heel strike/Initial contact : Begins the instant the heel touches the ground. At that time the pelvis is rotating forward,the hip is flexed at 30 deg. and is in neutral rotation and neutral abduction-adduction. The knee is almost fully extended and the ankle is in neutral position. Active muscles – hip extensors(breaking swing phase),knee flexors and extensors(stabilize knee),ankle dorsiflexors(preventing foot slap).

       Foot flat or loading response : 10-15% of gait cycle. Entire foot contact in ground. Shock absorbtion primary action in this period. The lower extremity joints are flexing to minimize upward excursion of pelvis,which also is beginning to decrease its forward rotation. Knee flexes to 15 deg. To aid in the cushioning process and the ankle plantarflexes to 15 deg. To attain ground contact. Active muscles : hip and knee extensors and ankle plantar flexors.

     Mid-stance : 15-20% of gait cycle. Body directly over weight bearing leg. Pelvis has ceased rotating forward while hip and knee in full extension and the ankle is at neutral with foot in ground contact. Active muscles : hip abductors and the ankle plantar flexors(begin activity of forward propulsion by push off),posterior tibial and peroneals( stabilize hind foot).

     Heel off/terminal stance : 20-25% of gait cycle. Heel of the weight bearing limb initially rises from the floor,weight is unloaded from the weight bearing limb and transferred to the opposite limb. Contralateral pelvis rotate forward,hip and knee in extension and foot neutral or plantarflexed. Active muscles : hip adductors and the plantar flexors.

    Toe off/ pre-swing : 5-10% of gait cycle. Knee of weight bearing limb flexes and prepares for the swing phase. Contralateral pelvis continues forward rotation.hip continues in neutral position,knee begins to flex reaching 35 deg.,ankle in full plantarflexion.

    Begins when the foot lifts off the ground and ends when the foot comes in contact with the ground. 40% of the gait cycle. Pelvis and limb tends to internally rotate,but the tibia externally rotates on the femur to improve knee stability prior to heel strike. This phase is furthur divided in to :

     Accelaration or initial swing : 5-10% of gait cycle. Begins the instant,the toes leaves the ground. The hip flexors accelerate the leg forward to catch up and eventually get in front of the body. The hip flexes to 20 deg. in neutral position and the knee achieves its maximum flexion of 70 deg. while the ankle moves up to 10 deg. plantarflexion to maintain toe clearance.

  Active muscles : hip flexors and adductors which are advancing the limb and ankle dorsiflexors,which are beginning to bring the foot up. The knee flexion is caused passively by inertia of leg as the thigh is advancing rapidly.

     Mid-swing : 20-30% of gait cycle. In this the non-weight bearing limb passes directly beneath the body. The swinging limb advances to achieve a vertical tibial position with the knee flexed,while hip flexion increases towards 30 deg.,knee extension occurs passively reducing the flexion of initial swing from 70 deg. to 30 deg.,and the ankle and foot are brought up to neutral position. Active muscles : continued firing of foot dorsiflexors.

    Deceleration/terminal swing : 5-10% of the gait cycle. The limb decelerates and is in a position of extension preparing for heel strike. The pelvis rotates forward,hip flexion reaches 30 deg.,the knee extends to near 0 deg,and the ankle maintains neutral position.

   Muscle activity picks up as the hip extensors begin to brake the forward swing and initiate extension. The knee flexors and extensors begin a synergitic action and stabilizing activity. Strong action of the dorsiflexors continue to hold the foot in neutral position.

THANK YOU

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