BIOMECHANICS OF GAIT
1. Describe the major phases of walking and the joint movements occurring during each
phase.
Gait Cycle: In walking each stride (a gait cycle) consists of two steps. The activities that occur from the point
of initial contact of one lower extremity to the point at which the same extremity contacts the ground again. (ie
the person takes 2 steps). For each limb there a stance phase, when the foot is in contact with the ground/floor,
and a swing phase when the foot is not in contact with the ground.
Walking is composed of seven phases. Stance phases include phases 1-4, while the swing phases comprises
phases 5-7. The phases of walking are:
Stance Phases
Begins at instant that one extremity contacts the ground (heel strike) and continues while the foot is in contact
with the ground until toe-off. Some portion of the foot is in contact with the ground at all times
Makes up 60% of the gait cycle during normal walking
1. Initial contact: Heel Strike
2. Opposite toe off: Occurs when the grounded foot is flat. It then passes through Midstance: Point at which
body weight is directly over the supporting lower extremity. E.g. The other foot (although still in air) is
passing the grounded leg.
3. Heel rise
4. Opposite initial contact
Swing Phases
Begins as soon as toe leaves ground and ceases just before heel strike or contact of the same extremity and
makes up 40% of gait cycle
5. Toe off: The leg accelerates during the initial swing after toe-off until midswing.
6. Feet adjacent: Midswing: Occurs when ipsilateral extremity passes directly beneath the body – follows the
period of maximum knee flexion and continues until the tibia is in vertical position (next phase)
7.
Tibia Vertical: The tibia hangs directly towards the ground then the leg decelerates in the terminal swing
between midswing and as the knee is extended in preparation for heel strike
A period of double-limb support occurs in walking, when the lower extremity of one side of the body is
beginning its stance phase and the other lower extremity is ending its stance phase. This is the time in which
both feet are in contact with the ground at the same time. This accounts for about 22% of the gait cycle. During
running, there is a "double-float" phase.
xJOINTS (For the 1 limb at these stages)
Stance Phases
1. Initial contact: Hip: Flexion/ Knee: Flexion/ Ankle: Plantarflexion (pushing down on ground).
2. Opposite toe off: Hip: Flexion to extension/ Knee: Flexion to extension/ Ankle: Plantarflexion to
dorsiflexion. (SO ALL NEUTRAL)
3. Heel rise: Hip: Extension to neutral/ Knee: Flexion/ Ankle: Plantarflexion
4.
Opposite initial contact: Hip: Neutral (may be some extension)/ Knee: Flexion/ Ankle: Dorsiflexion
Swing Phases
5. Toe off: Hip: Flexion/ Knee: Flexion and Extension/ Ankle: Plantarlexion becoming Dorsiflexion
6. Feet adjacent: Hip: Flexion / Knee: Flexion/ Ankle: Dorsiflection
7. Tibia Vertical: Hip: Felxion/ Knee: Flexion changing to extension/ Ankle: Neutral
2. Identify the functions of the four major lower limb muscle groups during walking.
The muscle and joint movements during each phase of walking.
The following show the average of a normal population, the speed of the gait and the individual can cause
variation.
STANCE PHASE
Initial Contact (Heel Strike)
Joint
Motion
Muscle
Flexion
Hamstrings
Hip
Adductor magnus
Gluteus maximus
Flexion
Quadriceps
Knee
Plantarflexion
Tibialis anterior
Ankle
(pushing down on
Extensor digitorium longus
ground)
Extensor hallucis longus
Midstance (Foot Flat) whilst other limb toes off.
Joint
Motion
Flexion to extension
Hip
Flexion to extension
Knee
Plantarflexion to
Ankle
dorsiflexion
Muscle
Gluteus maximus
quadriceps
Soleus, gastrocnemius, plantarflexors
Midstance to Heel-off
Joint
Hip
Knee
Ankle
Motion
Extension
Flexion to extension
Plantarflexion
Muscle
Hip flexors
No activity
Posterior leg muscles
Heel Rise
Joint
Hip
Motion
Extension to neutral
Knee
Ankle
Flexion
Plantarflexion
Muscle
Iliopsoas
Adductors, quadriceps
Quadriceps
Posterior leg muscles
SWING PHASE
Toe Off and Acceleration to midswing
Joint
Motion
Flexion
Hip
Flexion and extension
Knee
Plantarflexion
Ankle
becoming Dorsiflexion
Feet Adjacent (Midswing) and Deceleration
Joint
Motion
Flexion
Hip
Extension and flexion
Knee
Neutral
Ankle
Muscle
Iliopsoas, gracilis, sartorius
Biceps femoris, Sartorius, Gracilis
Tibialis anterior, extensor digitorum longus,
extensor hallicus longus
Muscle
Gluteus maximus
Quadriceps, hamstrings
Tibialis anterior, extensor digitorium longus,
extensor hallicus longus
Hip Muscles
 Gluteus maximus is active just before the end of swing and this activity continues into the beginning of the
stance phase, probably to control hip flexion (keeping the trunk erect).
 Gluteus medius acts throughout the stance phase to prevent the pelvis dropping to the unsupported side.
Weakness in the hip abductors may result in Trendelenburg's Gait. In Trendelenburg's gait, the pelvis
"drops" to the unsupported side, and as an adaptation, the patient often leans the trunk over towards the
supported side to compensate.
 Iliopsoas is most active during the swing phase to produce hip flexion.
 The group of lateral hip rotators is active during the first part of the swing phase when the pelvis is
rotating about the supporting hip. Lateral hip rotation of the swinging limb occurs to keep the toes pointed
in the right direction. The internal hip rotation occurring on the supported side is counteracted by opposite
rotation on the unsupported side.
Thigh Muscles


Quadriceps femoris has two main peaks of activity; just after heel strike to prevent knee flexion via
eccentric contraction, and at the time of toe-off, it also acts to prevent knee flexion when gastrocnemius is
active and therefore tending to cause knee flexion.
Hamstring activity just before heel-strike will aid in decelerating the lower limb at the hip, while continued
activity after heel-strike will aid knee stabilisation. Sometimes, the hamstrings are active towards the end of
the stance phase, presumably to prevent hip flexion.
Leg Muscles
 Gastrocnemius and soleus are active during mid stance to control the rate of dorsiflexion that occurs as the
result of the forward progression of the trunk. Gastrocnemius and soleus is most active between heel-off
and toe-off when the ankle is plantar flexing during the final propulsive phase.
 The anterolateral muscle group of the leg has some activity throughout the walking cycle but is most
active just after heel-strike when it acts eccentrically to control the rate of plantar flexion. Tibialis anterior
may also control hind-foot pronation that occurs just after heel-strike. These dorsiflexors are also active
during the swing phase to prevent the toes "stubbing" on the ground. Anybody with dorsiflexor weakness,
commonly from damage to the common fibular nerve, will exhibit two obvious gait abnormalities. Firstly,
"foot slap" will result from lack of foot/ankle control at heel strike, and; secondly, a high knee lift will be
developed to prevent the toes dragging on the ground/floor
 Fibularis longus is most active during mid-stance when it may be responsible for returning the hind-foot to
the neutral position and then maintaining this position.
Foot Muscles

Intrinsic plantar foot muscles may be active during the stance phase to aid in arch support.
In summary, the Quadriceps act to prevent knee collapse at heel strike, hamstrings act to control knee
extension at the end of swing, gastrocnemius and soleus act to control dorsiflexion during stance and the
anterolateral leg muscles (dorsiflexors) act to lift toes away from floor during swing and control plantar
flexion at heel strike.
3. Predict the gait abnormalities that may result from damage to the major nerve
supplies to the foot.
Some gait abnormalities are so characteristic that they have been given descriptive names:
 Propulsive gait: A stooped, rigid posture, with the head and neck bent forward.
 Scissors gait: Legs flexed slightly at the hips and knees, giving the appearance of crouching, with the knees
and thighs hitting or crossing in a scissors-like movement.
 Spastic gait: A stiff, foot-dragging walk caused by one-sided, long-term, muscle contraction.
 Steppage gait: Foot drop where the foot hangs with the toes pointing down, causing the toes to scrape the
ground while walking.
 Waddling gait: A distinctive duck-like walk that may appear in childhood or later in life.
Gluteus medius gait:
 Paralysis of one gluteus medius muscle.
 Gluteus medius normally stabilises the hip and pelvis by controlling the drop of the pelvis during singlelimb support.

Pelvis and trunk falling excessively on the inhibited gluteus medius activity side of the body.
Gluteus maximus gait:
 Normally, the gluteus maximus controls stability in sagittal plane and restraint of forward progression.
 Backward lean.
Quadriceps paralysis:
 Easily compensated for if person has normal hip extensors and plantarflexors.
 quadriceps are needed during gait at initial contact and loading response when there is a flexion moment
acting at the knee.
Plantarflexor paralysis:
 Plantarflexors = Gastrocnemius, soleus, flexor digitorium longus, tibialis posterior, plantaris and flexor
hallucis longus.
 Calcaneal gait pattern: Greater than normal amounts of ankle dorsiflexion and knee flexion during stance
and less than normal step length on affected side.
 Need to compare left and right side step lengths.
Severing the common fibular nerve:
 Common fibular serves the dorsiflexors of ankle and evertors of the foot (all muscles in anterior and lateral
compartments of the leg)
 Common fibular nerve is found just below the knee
 Foot-drop
 Impossible to make the heel strike the ground first as the foot falls into plantar flexion when it is raised off
the ground. So the patient has a high steppage gait: Raising the foot as high as necessary to keep the toes
from hitting the ground
 The foot comes down suddenly too: Producing a “clop” sound
Severing the tibial nerve
 Not common due to its protected position in the popliteal fossa
 Severance results in paralysis of the flexor muscles of the leg and intrinsic muscles of the sole of the foot.
 So unable to plantarflex foot or flex toes and there is also loss of sensation on sole of foot
Sciatica
 Results from nerve root compression by a prolapsed intervertebral disc.
 Causes shooting pain through the buttock and posterior thigh of the side affected.