Gait Cycle Summary

Gait Cycle

Learning Objectives

• Briefly consider the developmental aspects of becoming upright and bipedal.
• Understand the concept of the center of gravity and its location in the body.
• Define the key terms used for walking and the gait cycle.
• Describe the stages of the walking cycle and identify potential abnormalities.
• Understand the impact of the gait cycle on the center of gravity and muscle compartments in the lower limb.
• Touch on examples of pathologies or abnormalities in the gait cycle, including Trendelenburg.

Key Points of Upright Walking

• Bipedalism: Standing on two feet, maintaining an upright position, and walking.
• Walking can be seen as controlled falling, involving constant balance adjustments.
• Development of bipedalism is linked to hand dexterity, brain growth, and opposable thumbs.
• The gait cycle requires bony changes, joint structure, and musculature in the lower limb.
• Understanding the normal gait cycle is crucial for identifying pathological changes caused by injuries or neurological conditions.

Lower Limb Structure and Function

• Joint structure and musculature in the lower limb are designed for upright posture.
• Key muscle groups at the hip, knee, and ankle facilitate joint movement in the upright position.
• Upright posture allows for seeing, turning the head, and depth perception.
• Increased hand-eye coordination is associated with bipedalism.
• Vertebrae increase in size towards the pelvis to support weight bearing.
• Lower limb joints, such as the hip, knee, and ankle, exhibit structural adaptations for bipedalism.
• The ability to bear weight and transfer it between feet is essential for walking.
• Balance and equilibrium are crucial for maintaining locomotion during the gait cycle.

Childhood Development

• Newborns lack the ability to hold themselves upright or move around.
• Children develop through crawling, pulling themselves up, and then walking.
• Crawling provides a wide base of support for balance.
• The progression to upright posture combines physical growth and learning.
• Unlike human babies, some mammalian species can stand shortly after birth due to more developed muscular strength and neural development.
• Human babies typically start walking around age one after crawling and pulling up.
• Toddlers walk with feet and arms splayed apart for balance.
• The center of gravity is higher in children, requiring balance adjustments.

Standing and Forces

• In an anatomical position, gravity acts downwards while the ground provides upward force.
• The center of gravity, a theoretical balance point, is located just in front of the second sacral vertebra.
• Balance is maintained when the center of gravity line falls within the base of support.
• The hip, knee, and ankle joints are stable in the anatomical position due to the line of gravity.
• Movement during walking requires adaptations and changes in the center of gravity.
• Posterior calf muscles help maintain balance at the ankle joint.
• The feet's arches and flat shape aid in weight transfer and balance.
• Lack of muscle activity can lead to fainting due to inadequate venous return.

Walking Cycle Dynamics

• Walking involves shifting the center of gravity and balancing on one limb at a time.
• Reciprocal arm movements aid balance.
• The gait cycle is unique to each individual and influenced by body shape, emotions, footwear, and health.
• It involves rhythmic changes between weight-bearing and swing phases.
• Opposing movements of upper limbs counterbalance and maintain balance.

Terminology

• Step: Advancing a foot from toe push-off to heel strike.
• Step length: Distance from one foot strike to the next.
• Stride length: One complete cycle using both legs, approximately $1.5$ meters.

Stages of the Gait Cycle

• Stance Phase (60% of the cycle):
  • Heel strike: Initial contact with the ground.
  • Midstance: Foot flattens and makes full contact with the ground.
  • Toe off: Foot pushes off the ground.
• Swing Phase (40% of the cycle):
  • From toe off to heel strike of the same foot.
• Double Support:
  • Brief period when both feet are on the ground during toe off on one foot and heel strike on the other, typically only occurs during walking not running.

Weight-Bearing

• Heel strike: Weight is concentrated on the calcaneus.
• Midstance: Weight is distributed along the lateral foot and across the transverse arch, with the whole foot on the ground.
• Toe off: Weight shifts to the forefoot, with propulsion from the big toe, hallux, via flexor hallucis longus and brevis.

Swing Phase

• The ankle should be in a neutral position.
• The knee is slightly flexed to absorb force.
• The hip is flexed to bring the limb forward.

Muscle Contraction

• Anterior compartment muscles of leg (dorsiflexors) contract eccentrically to control lowering of foot from heel strike to mid stance.
• Double support occurs briefly during heel strike.
• Posterior calf muscles contract eccentrically in mid stance, then concentrically to push off.
• Hip is stabilized by gluteal muscles. We previously touched on how this test would work when we looked at Trendelenburg tests and hip musculture.
• During toe off: the ankle is plantar flexed. To prepare to swing leg the knee and hip are flexed, while the hip is stabilizing the pelvis.
• Eccentric and concentric contractions are balanced for foot stability and clearance.

Ankle and Knee

• During heel strike: dorsiflexors contract concentrically.
• During Mid Stance: anterior compartment muscles contract eccentrically, then posterior compartment muscles contract concentrically for push off.
• Neutral ankle position during swing phase for ground clearance.
• Knee flexion for clearance during swing phase.

Hip Muscles

*Hip flexors contract to bring the hip forward.
*Knee flexors (hamstrings) contract at the start of swing.
*Quads take over to extend knee.

Overall Movement

• Rhythmic oppositional movement of arm and leg.
• Vertical displacement of head: $5$ cm.
• Lateral displacement: $5$ cm.

Running

• Both feet are off the ground simultaneously.
• The propelling limb is also the weight-bearing limb.
• More force is transmitted to the hip joint and femoral neck.
• Foot strike patterns vary; forefoot running involves landing on the metatarsal heads and absorbing force at the ankle.

Gait Analysis

• Velocity: Distance covered in a time period; clinically assessable (e.g., six-minute walk test).
• Cadence: Number of steps taken per minute; walking at $100$ steps/minute is moderate intensity, while $130$ steps/minute is vigorous.

Lower Limb Design

• Large joint surfaces (femur, tibia) for weight absorption.
• Deep-socketed hip joint with strong ligaments.
• Knee joint with strong ligaments for stability.
• Efficient hinge at the ankle joint.
• Arches of the foot (longitudinal and transverse) for weight distribution and push off.
• Muscles in the sole of the foot for balance and propulsion.
• Thick fat pads for cushioning.

Gait Deviations

• Evaluate deviations by comparing them with a traditional pattern of the gait cycle.
  *Pelvic tilt must be controlled.
  *Ankle muscle movements are vital for balance and propulsion.
  *Hip Flexion and Extension must be coordinated.

Causes

• Pain *Limited ranges of movement *Nerve damage
  • Central or peripheral nervous system disorders will change how muscles contract
  • Neural disturbances
    *Weakened Muscles

Gait Abnormalities

• Antalgic Gait: Short step length due to pain. Limping is common.
• Inadequate Foot Clearance: Occurs due to:
  • Unequal leg lengths.
  • Inability to flex the knee.
  • Tightness in gastrocnemius and soleus.
  • Weakness in dorsiflexors.
  • Compensations include flexing knee and arching or hitching of hip.
• Pelvic Instability: Weak hip musculature (gluteus medius and minimus) causes lurching and dropping of the pelvis. Waddling gait is a compensation.

Riddle of the Sphinx

• What goes on four legs in the morning, two legs at noon, and three legs in the evening?
• Answer: A human being
  • Crawling in infancy (four legs).
  • Bipedal walking at maturity (two legs).
  • Using a walking stick in old age (three legs).

Conclusion and Further Studies

• Understanding normal anatomy and potential abnormalities is crucial for gait analysis.
• Practice walking through the gait cycle to understand the movements of the foot, knee, and hip joint.