Introduction to the
Conventional Gait Model
Richard Baker
Professor of Clinical Gait Analysis
Blog: wwRichard.net
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Conventional Gait Model
Newington, Davis,Gage
Helen Hayes, Kadaba
Vicon Clinical Manager (VCM), Plugin Gait
Conventional gait model (Visual 3d)
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Conventional Gait Model
By far the most widely used and best
understood model in clinical gait analysis.
Widely used in more general applications.
Better validated than any other model.
Better standardised than any other model.
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Understanding the model
• Anatomical segment definition
• Theory of marker placement
• Placing markers on the ideal person
• Placing markers on less ideal people.
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Tibia11
Principal axis From knee joint centre to ankle joint centre
Reference pointLateral malleolus
Marker placement
• The system only sees the middle of the
marker (not the baseplate)
• Use landmarks as a guide and try and
visualise the lines and planes
• Always place markers on skin
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Pelvis18
Principal axis From one ASIS to the other
Reference pointMid point of PSIS
Right ASIS (Anterior superior iliac spine)
Left ASIS
Pelvis19
Principal axis From one ASIS to the other
Reference pointMid point of PSIS
Left PSIS (Posterior superior
iliac spine)
Right PSIS
Pelvis20
Principal axis From one ASIS to the other
Reference pointMid point of PSIS
Marker centres are a marker radius in front of ASIS
Need to tell software what the marker diameter is
Femur21
Principal axis From hip joint centre to knee joint centre
Reference pointLateral epicondyle
Lateral epicondyle
Femur23
Medio-lateral distance is a proportion of ASIS width
If InterASISDistance is measured and entered PiG will use this.
If not PiG will take measured distance between ASIS
Femur24
Anterior-posterio distance
If AsisTrocDist is entered then PiG will calculate a distance based on this and leg length.
If not the distance is calculated as a function of leg length only
Femur26
Proximal-distal distance
If AsisTrocDist is entered then PiG will calculate a distance based on this and leg length.
If not the distance is calculated as a function of leg length only
Tibia31
Principal axis From knee joint centre to ankle joint centre
Reference pointLateral malleolus
Lateral malleolus
Tibia34
Shank wand determines the coronal plane of the tibia
50% to 70% of distance from knee to ankle
Foot38
On second ray at level of “bump” on 1st cuneiform-metatarsal joint
A more distal marker may give erroneous dorsiflexion if foot deforms
Foot40
Foot rotation
offset
Plantarflexion offset
Line from heel to forefoot markers defines long axis of foot in horixontal plane
Foot41
Foot rotation
offset
Plantarflexion offset
Line from heel to forefoot markers defines long axis of in sagittal plane
(or check foot flat box)
Foot42
If foot not flat on the ground heel marker must be same distance from plantar surface as forefoot marker
Plantarflexion offset
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