1. GAIT ANALYSIS
WALKING: depends upon the repeated performance by the lower limbs of a sequence of motions which advance the body along a desired line of progression while also maintaining a stable weight bearing posture.
The effectiveness of walking will depend upon free joint mobility and muscle action.

2. Gait Cycle
Each sequence of limb action is called a gait cycle which involves a period of weight bearing (stance) and a period of self advancement i.e. swing.(i.e. the action of our limbs is reciprocal action ,when one leg is in stance the other leg is in swing)
Approximately 60% of time is spend in stance & 40% in swing.
The reciprocal action of the limbs is timed to trade their weight bearing responsibility during a period of double stance

3. Gait Parameter Definitions:
Base of Support is the distance between parallel lines intersecting the midpoint of each heel print
Line of Progression is a line located approximately at the center point between both feet along the walker’s path of progression
Foot Angle is the angle formed by the intersection of the line of progression and a second line, which is drawn through the midpoint of the heel and the space between the second and third tarsal

4. Gait Parmeter Definitions
Step Length =Distance between corresponding successive points of heel contact of the opposite feet
Rt step length = Lt step length (in normal gait)
Stride Length =Distance between successive points of heel contact of the same foot
Double the step length (in normal gait)
Cadence =Number of steps per unit time
Normal: 100 – 115 steps/min
Velocity = Distance covered by the body in unit time
Usually measured in m/s
Instantaneous velocity varies during the gait cycle
Average velocity (m/min) = step length (m) x cadence (steps/min)
Comfortable Walking Speed (CWS) =Least energy consumption per unit distance
Average= 80 m/min (~ 5 km/h , ~ 3 mph)

5. Functional Elements
Three are three components or functional elements of walking:
Progression
Standing Stability
Energy Conservation

6. Functional Elements
Progression: There are two main progressional forces:
1)The primary one is the forward fall of body weight as the ankle dorsiflexes beyond neutral and accelerates with heel rise.
2)The second generated by the contra lateral swinging limb starts with onset of single limb support The action is particularly important before the body is aligned for a forward fall.
The momentum generated by these two actions is preserved at the onset of the next stance phase by floor contact with the heel.
Thus throughout the stance the heel, forefoot and the ankle serve as a rocker which advance the body over the supporting foot.

7. Functional Elements
Standing Stability: Balance is challenged by two factors 1)body is top heavy & walking continuously alters the segment alignment.
During walking the body is divided into two functional units: Passenger(head ,neck, trunk)as they are carried, rather than contributing to the act the act of walking Locomotor unit (limbs joint by intervening pelvis).
Muscle action with the neck and the trunk is to maintain neutral vertebral alignment
Arm swing is a passive reaction to the momentum generated during walking

8. Functional Elements
2)Weight bearing stability is maximum when it’s 3 components are vertically aligned.
The skeletal architecture is designed for mobility, this means some stabilizing mechanisms are needed
Thus at the hip and knee joints ligaments and the muscles in the limbs help to stabilize the joints
3)The ankle joint divides the foot in to a larger anterior portion and a smaller posterior portion, thus the body wt vector should pass through the anterior part of the foot

9. Functional Elements
Energy Conservation: efficiency is energy expenditure per task performed. for walking it is oxygen used per meter travelled
Oxygen is consumed as the muscles contract during walking. so the energy can be conserved by reducing the amount of oxygen consumed i.e. by reducing muscle activity
The muscle activity can be reduced by 1) substituting momentum in place of muscle action whenever possible, displacement of body from the line of progression is minimized .

10. Functional Elements
Optimum use of momentum occurs during the persons natural gait velocity which requires a least energy expenditure per meter travelled
Both slower and faster pace increase energy cost
Minimization of body displacement from the line of progression is accomplished by coordinating the pelvic, knee and ankle motion to keep the relative limb length relatively constant during stance. At the onset of double stance body height is the lowest as the limbs are diagonal. The highest position is in middle of the single stance when the limb is vertical
To reduce these extremes normal gait cycle involves 3 pelvic motions: lateral drop, transverse rotation and anterior tilt

11. Joint Motion
The interplay of progression ,standing stability and energy conservation result in complex and continually changing relationship between the various limb segments as the body advances over the supporting foot and the toe is lifted to clear the ground.
Each joint performs a repetitive pattern of motion
There are three joints involved in walking:
Ankle
Knee
Hip

13. ANKLE JOINT
The ankle joint is formed where the foot and the leg meet. The ankle is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus bone in the foot.
The bones of the ankle, called tarsal bones, consist of the talus, calcaneus (heel), navicular, cuboid, medial or internal cuneiform, middle cuneiform, and lateral or external cuneiform
The ankle joint is bound by the strong deltoid ligament and three lateral ligaments: the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament
The ankle joint permits planter flexion ,dorsiflexion ,inversion eversion (foot)

14. Motion At Ankle
Two periods of planter flexion and dorsiflexion are experienced in each gait cycle.
At onset of stance ankle has 90 degree position w.r.t foot(neutral)
As heel is loaded ankle drops into 10 degrees of PF
Then action is reversed and reaches 1o degrees of dorsiflexion.
The PF is resumed reaching 20 degrees by the end of stance(double stance)
With toe-off foot is raised to neutral dorsiflexion and is maintained in this position throughout the swing phase

15. Motion At Ankle

17. KNEE JOINT
The knee is essentially made up of four bones. The femur, which is the large bone in your thigh, attaches by ligaments and a capsule to your tibia. Just below and next to the tibia is the fibula, which runs parallel to the tibia. The patella, or what we call the knee cap, rides on the knee joint as the knee bends.
When the knee moves, it does not just bend and straighten, or, as it is medically termed, flex and extend. There is also a slight rotational component in this motion. The knee muscles which go across the knee joint are the quadriceps and the hamstrings. The quadriceps muscles are on the front of the knee, and the hamstrings are on the back of the knee. The ligaments are equally important in the knee joint because they hold the joint together. the bones support the knee and provide the rigid structure of the joint, the muscles move the joint, and the ligaments stabilize the joint.

18. Motion At Knee Two phases of flexion and extension
Beginning in full extension(flexed 5 degrees). It rapidly flexes to 15 degrees.
Then it progressively begins to extend .
Within onset of double stance it again begins to flex.
The action continues in swing till it reaches 60 degrees before extension is resumed

19. Motion At Knee

21. HIP JOINT
The hip joint is the joint between the femur and acetabulum of the pelvis and its primary function is to support the weight of the body in both static (e.g. standing) and dynamic (e.g. walking or running) postures.
The hip joint is reinforced by five ligaments, of which four are extracapsular and one intracapsular
The hip muscles act on three mutually perpendicular main axes, all of which pass through the center of the femoral head, resulting in 3 movements: Flexion and extension around a transverse axis (left-right); lateral rotation and medial rotation around a longitudinal axis (along the thigh); and abduction and adduction around a sagittal axis (forward-backward) and circumduction

22. Motion At Hip
Only a single arc of hip extension and flexion occurs fro each gait cycle.
As the foot strikes the ground the hip is in 30° of flexion.
Throughout the stance there is progressive extension into 10° of hyperextension.
Then flexion begins in terminal double stance and continues in most of the swing.
When the 30° posture is reached it is maintained until stance resumed

23. Motion At Hip

24. Gait Cycle
Stance Phase: To allow progression while maintaining weight bearing stability the limb performs the distinct tasks that define the phases of stance.
The stance phase is further divided into five stages
Initial contact
Loading response
Mid Stance
Terminal Stance
Pre swing

25. Initial Stance
Of primary concern is the way the foot strikes the floor
Heel will strike the floor at an angle of 25°
The ankle is in neutral position(PF 3°)
Knee is extended between o to 5 °of flexion
Hip is flexed 30°
The body weight vector passes through the heel which is anterior to both knee and hip.
Three torques are generated: ankle PF, Knee extension, hip flexion

26. Initial Stance
Control of both knee and ankle is critical to have a normal heel strike
The ankle motion is dependent on the free joint mobility and the pretibial muscles
Knee extension is accomplished by the quadriceps action
Hip does not influence mode of floor contact but determines the angle between foot and floor

27. Initial Stance
stance
wt vector

28. Loading response
Acceptance of body weight in such a manner that assures limb stability and still perform progression is the goal of this stage. The action at the ankle precedes and contributes to the knee action.
Ankle: After floor contact by the heel the foot drops into 10 of PF in a controlled manner. The action is initiated when the body weight is applied at the talus and the floor contact is still at the calcaneus (heel bone).An unstable lever will result from difference in length between these two points. Strong action by the pretibial muscles retards the terminal arc of ankle planter flexion so forefoot contact is gradual .thus heel strike is heard but no foot slap

29. Loading response
Knee: flexion of knee is to 15 is initiated by heel rocker action. As the pretibial muscles contract to restrain ankle PF it also draws tibia forward this is rapid action and it advances the knee much faster than the thigh and trunk can follow. As result the body weight shifts posterior to the knee and a flexion torque is induced.
Two types of muscle actions result –increased quadriceps activity to restrain rate of knee flexion
No hamstring muscles are needed for knee hyperextension.

30. Loading response
Hip: little change in the body position occurs during the loading response.
stance

31. Mid Stance
Advancement of body and limb over a stationary foot is the functional objective of this gait phase
As the other foot is lifted from ground a period of single limb support begins, maximum stability is gained by having the foot stationary and in total contact with the floor
As the body weight advances the base of the weight vector moves from heel to forefoot
stance
stance

32. Mid Stance Ankle: At onset of single stance ankle is slightly PF by 5°
From this position there is gradual dorsiflexion, the basic arc is from -5° to 5° with 10° of DF being attained just as the heel rises to initiate terminal stance
The body vector moves anterior to the ankle

33. Mid Stance
Knee: knee flexion introduced during response increases to 18° just as single limb support is initiated
In the middle of mid-stance body wt vector moves anterior to the joint center so the need for active muscular control is terminated.
Quadriceps action is maximum at the onset of mid stance ,it then progressively declines as knee extends over vertical tibia
Once the vector becomes anterior to the knee axis ,extension stability is provided passively and the quadriceps relaxes.

34. Mid Stance
Hip :Progressive decline of hip flexion and entry in to extension allow trunk to remain erect while limb becomes more vertical

35. Mid Stance
Lifting the opposite limb removes support from that side of the body .The unsupported pelvis falls creating hip adduction in the stance limb. This is rapidly limited to 4 degrees and reduced by active abduction
Hip abductor muscle activity is intense throughout the mid stance while extensors are quiet.

36. Terminal Stance
Primary objective of TS is forward fall to generate a propulsive force.
Heel rise signifies on state of second phase of single stance.
Now forefoot serves as the rocker with the body falling forward of it’s area of support .
This creates a primary propulsive force for walking

37. Terminal Stance
Ankle: At onset of heel rise the ankle drops in to maximum dorsiflexion (10°) occurring in stance
Motion then reverses to 5° of PF by end of single limb support
Stability is accomplished by the triceps surae
With heel rise body vector is concentrated at the forefoot
The distance between the vector and ankle joint generates a maximum dorsiflexion torque
Both soleus and gastrocnemius respond vigorously to maintain ankle in neutral position and ceases as the weight is transferred to the other foot.

38. Terminal Stance Knee: maximum extension of knee between o to -5
At the end of the terminal stance the knee begins to flex .Body weight is rapidly falling towards the other limb
There is no quadriceps action for knee extension
Stability is gained from the body vector being anterior to the knee axis

39. Terminal Stance
Hip: Passive extension of the hip jt continues as the body wt advances over the supporting foot and the trunk remains erect by the end of stance there is 10 degrees of hyperextension
There is no hip extensor activity during terminal stance
As the body wt begins to fall forward the other limb the hip abductors terminate their action ,for passive abduction is induced.

40. Terminal Stance

41. Preswing
Preparation of the limb for swing is the purpose of action that occur during the preswing phase.
Floor contact by the other foot initiates this interval of terminal double support
Rapid transfer of body wt to the limb allows the desired action to follow.
The critical area of response is the knee

42. Preswing Ankle: there is rapid ankle PF to a 20 position
Knee: There is rapid passive flexion to 45 which occurs because the body wt is rolled so far forward of the forefoot rocker that the tibia is no longer stable.
Hip: flexion of hip jt is initiated with recovery from hyperextension to neutral that occurs during this phase.

43. stance
stance
stance
stance
stance

44. swing
Lifting the foot from the ground and limb advancement followed by preparation for stance are the objectives of three phases of swing

45. Initial Swing
Recovery of the trailing position is the task that is accomplished
This involves two critical actions flexion of both hip and the knee.

46. Initial Swing
Ankle : DF of the ankle is initiated but only half of the 20 PF present at toe off is recovered at this time
Thus toe clearance is not dependent on the ankle dorsiflexion during initial phase of the swing.
The muscles contract quickly to lift the foot.
Knee: the flexion increases to 60
No dominant flexion force
Hip: from the neutral position at toe-off the hip rapidly flexes to 20

47. Mid Swing
As the limb advancement continues the changes in the tibial alignment make foot control critical for floor clearance

48. Mid Swing Hip: maximum flexion to 30 is reached by iliacus action
Knee: relaxation of the flexor muscles allows the knee to extend passively ,which accelerates advancement of leg and foot
By the end of mid swing knee flexion equals that of hip flexion
Ankle: Dorsiflexion to neutral is accomplished and maintained.

49. Terminal Swing
Advancement is terminated and the leg is prepared for stance.
Knee extension is the critical event.

50. Terminal Swing
Ankle: continued neutral dorsiflexion is the basic posture, but the foot may drop in to slight PF (3° to 5°) at the end of the phase.
Knee: The extension of the knee to neutral continues(0° t 5°).The quadriceps provide the necessary extensor force
Hip: The 30° of flexion attained in flexion is maintained .For this purpose iliacus continues to support limb weight while hamstrings prevent further motion.

52. Gait cycle summery Joint angles Ankle Joint Knee Joint Hip Joint
Weight Vector
Initial Stance
neutral
5 degree flextion
30 degree flexion
Passes through heel,anterior to knee and hip
Loading Response
10 degree PF
15 degree PF
Almost same
Heel,posterior to knee,hip
Mid Stance
10 degree DF
18 degree flex
Entry into extension
Heel and then through forefoot
Terminal Stance
5 degree DF
0-5 degree extension
10 degree hyperextension
forefoot
Pre Swing
20 degree PF
45 degree flex
Entry into flex
Passes through the Tip of forefoot
Initial swing
60 degree flex
20 degree flex -
Mid swing
30 degree flex
Terminal swing
0-5 degree
5 degree flex
Gait cycle summery

53. Gait cycle summery

54. Determinants of Gait : (1) Pelvic rotation:
Forward rotation of the pelvis in the horizontal plane approx. 8o on the swing-phase side
Reduces the angle of hip flexion & extension
Enables a slightly longer step-length w/o further lowering of CG

55. Determinants of Gait : (2) Pelvic tilt:
5o dip of the swinging side (i.e. hip adduction)
In standing, this dip is a positive Trendelenberg sign
Reduces the height of the apex of the curve of CG