Gait analysis definitions

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  • 1. ANALYSIS AND INTERPRETATION OF GROUND REACTION FORCES IN NORMAL GAIT Gait analysis, the systematic analysis of locomotion, is used today for pre-treatment assessment, surgical decision making, postoperative follow-up, and management of both adult and young patients. Visualising ground reaction forces helps us understand the effect they are having on the body in walking. Kinetics by definition deals with those variables that are the cause of the specific walking or running pattern that we can observe or measure with cameras. Transducers have been developed that can be implanted surgically to measure the force exerted by a muscle at the tendon. Comparing the vertical ground reaction force signal components during stance phase in a healthy and unhealthy leg, specifically gait pathology resulting from a fused hip, the signals were recorded and proved to differ significantly because the remaining normal segments of the attacked extremity are only able to partially compensate for the loss of the hip joint function. Comparing the vertical ground reaction force signal components in healthy subjects and patients with cerebellar ataxia, an appreciable irregularity and weak formation of the initial phase of the force signal in the patient were found to be relevant. In gait, as well as running, ground reaction force signals reflect an increase in the movement speed through the even larger increase in peak values and a shortening of signal duration. Taking one limb, every gait cycle encompasses two main phases: so called “stance” phase (60% of gait cycle), where the contact with the ground occurs, and the “swing” phase (40% of gait cycle) during which the foot is not in contact with the ground. The stance phase starts with the “heel strike” (HS) at which point the contact with ground is made. After the heel touches the ground, the foot is carefully controlled to come down towards the ground and provide a stable support base for the rest of the body. This is termed “foot flat” (FF). Then, the whole body rolls over the foot with the ankle acting as a pivot joint and the hip joint is placed directly above the ankle joint at “midstance” (MD). From that point onwards the purpose of lower limb is to propel the body centre of mass forward during the push off phase with an important time instant occurring when the heel loses contact with the ground at “heel rise” (HR). As the foot leaves the ground, it is usual for the toe to be the last point of contact, hence the end of the stance phase is often referred to as “toe off” (TO). For normal subjects walking at their preferred speed on a level surface, the stance phase can take approximately 62% of the complete gait cycle (100%). If each foot is in contact with the ground for 62% of the cycle, there must be a 12% period of the cycle where both feet are in contact with the ground at the same time. This very important phase is the “double support period” and represents the changeover and fine control for the smooth transition between limb support on the left and limb support on the right. When walking velocity is increased the period of double support will be reduced. Eventually a velocity will be reached when there is no double support and this is the Olympic classification for “running”. As people start to run faster, the period of double support becomes negative and there is a flight phase.
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Gait analysis definitions

  1. 1. Gait Analysis Definitions PTHE 1581
  2. 2. Objectives Define the terms for gait analysis as described by Rancho Los Amigos Observational Gait Analysis Briefly describe what is happening in the lower limbs during each phase of gait
  3. 3. Rancho Los Amigos Terms Stance:  Weight Acceptance  Initial contact  Loading response g p  Single Limb Support  Midstance  TTerminal Stance lS Swing:  Sing Limb Advancement  Pre-Swing  Initial Swing  MdS Mid Swing  Terminal Swing
  4. 4. Other Terms (from Oatis)  Rancho Los Amigos terms are in parentheses; they do not correlate perfectly lt f tl  Stance:  Ground contact (initial contact) ( )  Foot flat (loading response to midstance)  Heel off (midstance to terminal stance)  Contralateral ground contact (terminal stance) C l l d ( i l )  Toe off (pre-swing)  Swing: g  Early swing (initial swing)  Mid swing (Mid swing)  L t swing (T Late i (Terminal swing) i l i )*** We will NOT be using this terminology in class, this information is for your reference only ***
  5. 5. Phases of Gait The following slides give a brief description of what happens at the hip, knee, and ankle during NORMAL gait
  6. 6. Initial Contact (IC) Foot makes contact with the ground  The hip is in 20 degrees of flexion  The knee is in 5 degrees of flexion  The ankle is in 0 degrees of dorsiflexion
  7. 7. Loading Response (LR) Shock absorbtion  Hip is in 20 degrees of flexion  Knee is in 15 degrees of flexion  Ankle is in 5 degrees of plantarflexion  Foot pronates
  8. 8. Mid Stance (MSt) The body moves forward over the foot  Hip is in 0 degrees flexion  Knee is in 5 degrees flexion  Ankle is in 5 degrees dorsiflexion
  9. 9. Terminal Stance (TSt) The body moves past the foot.  Hip is in 20 degrees extension (apparent motion; some of this comes from pelvic rotation)  Knee is in 5 degrees of flexion  Ankle is in 10 degrees of dorsiflexion
  10. 10. Pre-SwingPre Swing (PSw) Weight is being transferred to the other limb  Hip is in 10 degrees hyperextension (apparent)  The knee is in 40 degrees of flexion  The ankle is in 15 degrees of plantarflexion  The first metatarsophalangeal joint is in 60 degrees of dorsiflexion
  11. 11. Initial Swing (ISw) Thigh begins to advance past the stance thigh and leg  Hip is in 15 degrees of flexion  Knee is in 60 degrees of flexion  Ankle is in 5 degrees of plantarflexion
  12. 12. Mid Swing (MSw) Leg has also advanced past the stance limb  Hip is in 25 degrees of flexion  Knee is in 25 degrees of flexion (perpendicular to the ground)  Ankle is in 0 degrees dorsiflexion
  13. 13. Terminal Swing (TSw) The leg extends to provide length to the step  The hip is in 20 degrees of flexion  The knee is in 5 degrees of flexion  The ankle is in 0 degrees of flexion

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