Gait Terminology & Biomechanics

• These notes cover gait terminology, osteokinematics, kinetics, muscle actions, and changes with aging, essential for accurate gait assessment, documentation, and communication in healthcare.

Gait Terminology and Descriptors

• Human gait propels the body's center of mass forward along a path, maintaining stability.
• This process prevents injury, maximizes efficiency, and absorbs impact.
• Key tasks in gait are weight acceptance, single leg stance, and swing leg advancement.
• Requirements for gait include sufficient muscular strength, postural control, and adaptability to environmental changes.
• Physical therapists assess gait patterns during examinations, interventions, and reassessments.
• The gait cycle is the sequence from heel strike to the next heel strike of the same foot.
• Terminology includes stance phase (60% of gait cycle) and swing phase (40% of gait cycle).
• Rancho Los Amigos terminology is current, while traditional terminology is also used to describe gait.

Osteokinematics of Walking

• Kinematics describes motion without regard to forces, focusing on osteokinematics of lower extremity segments during gait.
• The presentation will cover motion in the pelvis, trunk, upper extremities, and lower extremities during weight acceptance, single limb stance, and limb advancement.
• The body's center of mass (CoM) displaces vertically (5 cm rise and fall) and laterally during gait.
• The pelvis normally rests in 10 degrees of anterior tilt, which changes during Terminal Stance and Terminal Swing.
• Pelvic rotation in the transverse plane facilitates smooth walking and efficient gait.
• Pelvic motions are often subtle (5 degrees), but excessive motions like hip hike or drop are noticeable.
• The position and movements of the head and trunk are influenced by CoM displacement and pelvic movements.
• Upper trunk/shoulder girdle rotates in the opposite direction to the pelvis.
• Arms act as counterweights, producing shoulder flexion and extension, with amplitude increasing with walk speed.
• During weight acceptance, the reference limb absorbs weight, increasing knee flexion and ankle plantarflexion through eccentric contractions.
• Hip extensors limit hip flexor moment.
• Single limb stance involves controlling forward progression while maintaining stability.
• The pelvis rotates posteriorly, hip extends up to 15 degrees, and ankle dorsiflexion increases.
• The ground reaction force causes hip extension.
• Eccentric contraction of plantarflexors controls increasing dorsiflexion
• Swing phase involves advancing and positioning the swing limb
• Hip moves from extension to flexion, knee flexes, and ankle dorsiflexes for foot clearance.
• The subtalar joint (STJ) moves from supination at initial contact to eversion during stance, then inverts again before pre-swing
• This rolling motion accommodates changing surfaces.
• Gait involves changing joint angles and muscle actions, requiring PTs to understand typical movements.

Kinetics of Walking

• Kinetics studies forces during the gait cycle, specifically ground reaction forces (GRF) and resulting moments.
• Internal muscular forces produce movement and generate torques, while external GRF produces moments around joints.
• Gravity pulls the body downward; the ground provides an upward reaction force (GRF) as key external force.
• Ground reaction forces have vertical, anterior-posterior, and medial-lateral components that change through the gait cycle.
• The composite GRF acts on the body at the point of contact and travels to the center of mass.
• If GRF's line of action is aligned to one side of a joint, it creates a rotatory moment (torque).
• At heel strike, GRF passes posterior to the hip, knee, and talocrural joints.
• This creates an extensor moment at the hip, a flexor moment at the knee, and a plantarflexion moment at the ankle.

Moments and Muscle Actions

• Ground reaction forces in gait produce moments that are opposed by muscle forces during normal gait
• Kinematics involves motions, kinetics is the forces
• Understand the ground reaction force in relation to the extremity joints and resulting moments
• Ground reaction forces are only present when the limb is in contact with the ground
• First, the heel strikes the floor and the ground exerts a reactional force that falls at the hip and knee joints but behind the angle, leading in hip flexion ,knee extension and plantar flexion that hip and knee extensors counteracted by the ankle dorsiflexors
• As the body progresses during the loading response the ground reacition forces produces hip flexion and plantar flexion; there will be also a flexion moment at the knee that the knee extensores must counteract
• In Midstance, the ground reaction force produces hip extension which requires minimal muscle action and a dorsi flexión that ankle plantar flexors counteract
• In Terminal Stance, the ground reaction force causes inherent joint stability, and is counteracted by plantar flexors.
• For Pre-swing, Hip adductors counteract hip extension
• The ground produces abduction or adduction moments on the lower extremity, otherwise varus and valgus, that the body avoids during single leg stance
• At initial contact The ground reaction force passes through the hip joint controlling foot placement

Changes in Gait with Aging

• Pediatric gait begins between 11 and 15 months with an immature pattern that is uneven.
• It has an uneven step length, increased hip, knee flexion, and increased hip abduction with external rotation.
• Kuo and Ulrich theorized that the high guard position helps control balance, preventing falls
• New walkers also present less pelvic mobility, while these and leg decreased length affect stride length and increase cadence
• Gait strategies decrease over time
• Mature gait patterns in children are well-established by age seven and resemble an adult; they present five characteristics
• 1. ability to maintain stability Adequate foot clearance in swing phase Foot pre-positioning to contact ground at correct heel strike There are challenges that aging presents; as Sarcopenia increases there are cognitive defeats that affects velocity
• Geriatric characteristics affect stability and coordination
• Changes start to occur from 60 to 65 years
• Integumentary, musculoskeletal, cardiovascular, and muscular components can be affected; these are Epidermal atrophy, osteoporosis, decreased cardiac output and muscle atrophy
• There are three systems of balance of stability that can be affected
• --Somatic System, Vision System and the Vestibular System
• Decline in spatio-temporal gait parameters is mainly due to imbalance and weakness in the muscles of the foot
• As PTs we can implement gait strategies effective that improve mobility and quality of life in older adults
• --By understanding gait alterations is effective on how to improve the quality of life
• Gait disturbances can be observed and we can classify mobility during home and community activities to avoid risk of falls