lecture 1 Gait analysis .pdf

Gait analysis Gait is the medical term to describe human locomotion, or the way that we walk. Interestingly, every individual has a unique gait pattern. A person’s gait can be greatly affected by injury or disease process. By evaluating the gait pattern of an individual, a therapist can determine s...

Gait analysis Gait is the medical term to describe human locomotion, or the way that we walk. Interestingly, every individual has a unique gait pattern. A person’s gait can be greatly affected by injury or disease process. By evaluating the gait pattern of an individual, a therapist can determine specific weaknesses and adjust rehabilitation programs to address these issues. Definition of normal gait Physiological Definition: It is a mechanism which depends upon closely integrated action of the subjects, bones, muscles and nervous system (including peripheral and central nervous system) The degree of integration determines the different gait patterns. Any defect of any part of them or all of them will lead to pathological gait. Mechanical definition: It is a form of bipedal locomotion as there is an alternating action between lower extremities. One leg is in touch with the ground for restraining, supporting and propulsion. The other leg is in swing phase for creating a new step forward. So, gait is the result of a series of rhythmic alternating movement of arms, legs, and trunk which create forward movement of the body. Prerequisites of gait: 1. The ability to support or assume upright position. (the ability to maintain head, arms, and trunk HAT against gravity) 2. The ability to maintain balance in an upright position during static and dynamic situation. 3. The ability to develop or create new step forward through controlling of foot movement to achieve safe ground clearance and gentle heel contact. N.B: HAT constitute 75% of total body weight. Phases of Gait cycle Phases of gait Gait cycle: is used to describe the complex activity of walking, or our gait pattern. This cycle describes the motions from initial placement of the supporting heel on the ground to when the same heel contacts the ground for a second time. At normal adult walking speeds, one cycle lasts 1 second and has a length of 1.4 meters. During one gait cycle, each extremity passes through two phases, a single stance phase and a single swing phase. I-Stance Phase: Is defined as the interval in which any part of the foot of one extremity is in contact with the ground (60% of the gait cycle) and it ends when the reference foot lifts off the ground. So, it is called “the supporting phase” or “weight bearing phase”. stance phase Stance Phase is divided into 5 phases: 1- Initial contact (heel strike): Initial contact is an instantaneous point in time only and occurs the instant the foot of the leading lower limb touches the ground. This phase occurs at about 0%- 2% of GC. The heel is usually the foot section that makes initial contact, but other parts of the foot may contact the ground first in the presence of some pathologic conditions. 2- Loading response (flat foot): The loading response phase occupies about 2%-10% of the GC and constitutes the period of initial double stance. During loading response, the foot comes in full contact with the floor, and body weight is fully transferred onto the stance limb. During this phase, the body’s impact forces with the ground are absorbed. 3- Mid stance Mid-stance represents the first half of single support, which occurs from the 10%- 30% of the GC. It begins when the contra-lateral foot leaves the ground and continues as the body weight travels along the length of the supporting lower limb until it is aligned over the forefoot. In this phase the body’s COM moves directly over the foot. 4- Terminal stance (heel off): Terminal stance constitutes the second half of single-limb support. It begins with heel of the reference foot rise and ends when the contra-lateral foot contacts the ground. Terminal stance occurs from the 30%- 50% of GC. 5- Pre-swing (toe off): Pre-swing occurs when only the toe of the reference limb is in contact with the ground. This phase called weight release or weight transfer. This phase occurs from 50%- 60% of GC. It is the terminal double stance interval. II-Swing phase: Is defined as the interval in which the foot of the reference limb is not in contact with the ground (40% of the gait cycle) and it ends just prior to heel strike of the same extremity. It denotes the time when the foot is in the air, so it is called “non- weight bearing period”. The swing period primarily is divided into three phases: Initial swing, mid-swing and terminal swing. swing phase 1- Initial swing (acceleration): It is the period from toe of the reference limb leaves the ground to the mid-swing of the reference limb. This phase is from 60%-73% of GC. 2- Mid-swing: It is period when the reference limb passes directly under the body. The reference limb reaches vertical tibial position just before the end of mid-swing. This phase is from 73%-87% of GC.  3- Terminal swing (deceleration): It is period from the end of mid-swing to the point just before initial contact. The knee is extending in preparation for new heel strike. This phase is from 87%-100% of GC. Intervals of gait cycle: Each gait cycle (stance and swing phase) is subdivided to intervals. I- Stance phase is subdivided into double limb support (initial double stance IDS, and terminal double stance TDS) and single limb support intervals: Intervals of gait cycle Double limb support (initial double stance and terminal double stance): Initial double stance: is the period when both feet are in contact with the ground. One foot is in initial contact and loading response and other foot is in pre-swing. Terminal double stance: in the late stance, the ipsilateral foot is in preswing, and the contralateral foot is in initial contact and loading response. Note: the terminal stance is divided into 2 parts, the first part is considered a single- limb stance and the second part is considered a double-limb stance. Single limb support SLS: is the period when only one foot is in contact with the ground (mid stance and terminal stance). In walking, this is equal to the swing phase of the other limb. It takes up to 40% of GC. II- Swing phase has one interval as one foot is not in contact with the ground and it takes up to 40% of gait cycle. Normal gait cycle