Gait Biomechanics 3 Determinants

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Biomechanics of the Gait : 3 Determinants of Gait :

Biomechanics of the Gait : 3 Determinants of Gait Dr. Dibyendunarayan Bid [PT] The Sarvajanik College of Physiotherapy, Rampura, Surat

Determinants of Gait:

Determinants of Gait First described by Saunders and coworkers in 1953 and elaborated on by Inman & colleagues in 1981. 7/2/2012 dnbid71@gmail.com 2

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The determinants are supposed to represent adjustment made by the pelvis, hips, knees, and ankles that help to keep movement of the body’s COG to a minimum. The determinants are credited with decreasing the vertical and lateral excursions of the body’s COG and therefore decreasing energy expenditure and making gait more efficient (Fig.14-22). 7/2/2012 dnbid71@gmail.com 3

Fig 14-22. The vertical displacement of the body’s COG produces a smooth sinusoidal curve in normal walking. The lowest point in the curve is during the period of double support. The highest point in the curve coincides with midstance when the trunk is directly over the stance extremity. The drawing shows the lowest and highest points in the curve.:

Fig 14-22. The vertical displacement of the body’s COG produces a smooth sinusoidal curve in normal walking. The lowest point in the curve is during the period of double support. The highest point in the curve coincides with midstance when the trunk is directly over the stance extremity. The drawing shows the lowest and highest points in the curve. 7/2/2012 dnbid71@gmail.com 4

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The 6 determinants are: Lateral pelvic tilt in the frontal plane, Knee flexion during stance, Knee interactions, Pelvic rotation in the transverse plane and, Physiological valgus of the knee. 7/2/2012 dnbid71@gmail.com 5

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The order of presentation of the determinants that follows is based on their function and is not necessarily related to the order in which they appear in the gait. 7/2/2012 dnbid71@gmail.com 6

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The first 4 determinants are supposed to help to keep the vertical rise of the body’s COG to a minimum. The 5 th determinant prevents a drop in the body’s COG, and the 6 th determinant reduces the side to side movement of the COG. 7/2/2012 dnbid71@gmail.com 7

Lateral Pelvic Tilt (Pelvic Drop in the Frontal Plane):

Lateral Pelvic Tilt (Pelvic Drop in the Frontal Plane) In single limb support the combined weight of HAT and the swinging leg must be balanced over one extremity. During this period the COG reaches its highest point in the sinusoidal curve. Lateral tilting of the pelvis (pelvic drop) on the side of the unsupported extremity (swing leg) keeps the peak of the rise lower than if the pelvis did not drop, because the drop produces a relative adduction of the stance hip in the stance phase and relative abduction of the swinging extremity (fig 14-23). 7/2/2012 dnbid71@gmail.com 8

Fig 14-23. Lateral pelvic tilt in the frontal plane keeps the peak of the sinusoidal curve lower than it would have been if the pelvis did not drop, because it produces adduction at the stance hip. Lateral pelvic tilt (drop) to the right is controlled by the left hip abductors.:

Fig 14-23. Lateral pelvic tilt in the frontal plane keeps the peak of the sinusoidal curve lower than it would have been if the pelvis did not drop, because it produces adduction at the stance hip. Lateral pelvic tilt (drop) to the right is controlled by the left hip abductors. 7/2/2012 dnbid71@gmail.com 9

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The tilting of pelvis is controlled by the hip abductor muscles of the stance extremity. For example, pelvic drop on the side of the right swing extremity is controlled by isometric and eccentric contractions of the left hip abductor muscles. 7/2/2012 dnbid71@gmail.com 10

Knee Flexion:

Knee Flexion Knee flexion at midstance when COG is at its highest represents another adjustment that helps to keep the COG from rising as much as it would have to if the body had to pass over a completely extended knee. 7/2/2012 dnbid71@gmail.com 11

Knee, Ankle, and Foot Interactions:

Knee, Ankle, and Foot Interactions Movements at the knee occur in conjunction with movements at the ankle and foot and are responsible for smoothing the pathways of the body’s COG so that it forms a sinusoidal curve. Combined knee, ankle, and foot movements prevent abrupt changes in the vertical displacement of the body’s from a downward to an upward direction. 7/2/2012 dnbid71@gmail.com 12

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The change from a downward motion of the COG at heel strike to an upward motion at foot flat (loading response) is accomplished by knee flexion, ankle plantarflexion, and foot pronation. These combined motions serve to relatively shorten the extremity and thus prevent an abrupt rise in the body’s COG after heel strike. If these motions did not occur in conjunction with each other, the COG would rise abruptly after heel strike as the tibia rides over talus. 7/2/2012 dnbid71@gmail.com 13

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Another stance in which knee ankle anf foot interactions play an important role is when the body’s COG falls after midstance. A combination of ankle plantarflexion, foot supination, and knee extension at heel off slow the descent of the body’s COG by a relative lengthening of the stance extremity. 7/2/2012 dnbid71@gmail.com 14

Forward and Backward Rotation of the Pelvis:

Forward and Backward Rotation of the Pelvis Forward and Backward Rotation of the Pelvis in the transverse plane accompany forward and backward movements of the lower extremities during gait (Fig. 14-24). Forward rotation occurs on the side of the swinging extremity with the hip joint of the weight-bearing extremity serving as the axis for pelvic rotation. 7/2/2012 dnbid71@gmail.com 15

Fig.14-24. Pelvic rotation in the transverse plane. The drawing shows left forward rotation of the pelvis on the side of the swinging extremity. The right hip joint serves as the axis of motion. THE BAR, which represents the pelvis , shows the apparent backward rotation that is occurring simultaneously on the right side of the pelvis. The pelvic rottation relatively lengthens the extremities and therefoe minimizes the drop of body’s COG that occurs at double support.:

Fig.14-24. Pelvic rotation in the transverse plane. The drawing shows left forward rotation of the pelvis on the side of the swinging extremity. The right hip joint serves as the axis of motion. THE BAR, which represents the pelvis , shows the apparent backward rotation that is occurring simultaneously on the right side of the pelvis. The pelvic rottation relatively lengthens the extremities and therefoe minimizes the drop of body’s COG that occurs at double support. 7/2/2012 dnbid71@gmail.com 16

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The pelvis begins to move forward at preswing and continues as the swinging extremity moves forward during initial swing. At the point of maximal elevation of the body’s COG in midstance, the forward pelvic rotation has brought the pelvis to a neutral position with respect to rotation. Forward rotation of the pelvis continues beyond neutral on the swing side through terminal swing to initial contact. 7/2/2012 dnbid71@gmail.com 17

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The total amount of rotation of the pelvis is small and averages about 4° on the swing and stance sides for a total of 8°. The result of pelvic rotation is an apparent lengthening of the lower extremities. The swinging lower extremity is lengthened in terminal swing by the forwardly rotating pelvis, and the weight bearing extremity is lengthened in preswing by the posterior position of the pelvis. 7/2/2012 dnbid71@gmail.com 18

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Therefore both the stance and swing extremities are lengthened as the COG descends to its lowest level in the period of double support. 7/2/2012 dnbid71@gmail.com 19

Physiological Valgus at the Knee:

Physiological Valgus at the Knee The physiologic valgus at the knee reduces the width of the BOS from what it would be if the femoral and tibial shafts formed a vertical line from the greater tuberosity of the femur (Fig. 14-25). Therefore, because the BOS is relatively narrow, little lateral motion of the pelvis is necessary to shift the COG from one lower extremity to another over the BOS. 7/2/2012 dnbid71@gmail.com 20

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Fig. 14-25. Physiologic valgus at the knee. 7/2/2012 dnbid71@gmail.com 21

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End of part - 3 7/2/2012 22 dnbid71@gmail.com

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