Gait and Lower Limb Mechanics

Question 1

Hip Joint

Answer 1

Posterior to flexion/extension axis of hip with tendency to hyperextend hip, which is counteracted by the iliofemoral ligament

Question 2

Knee Joint

Answer 2

Anterior to flexion/extension axis of knee
Tendency to hyperextend knee
Posterior capsule of knee, especially oblique popliteal ligament and cruciate ligaments counteract this

Question 3

Locking Mechanism of Knee

Answer 3

Passive mechanism: Medial condyle is longer articular surface → greater range of rotation on medial tibial plateau
When standing: Femur rotates internally (medially) on a fixed tibia upon full extension → Taut ligaments

Question 4

Ankle Joint

Answer 4

Anterior to flexion/extension axis of ankle
Tendency to fall forward/dorsiflex at ankle
No appropriate ligaments counteract these movements, so requires muscular effort from the soleus and gastrocnemius muscles, which consist mostly of type I muscle fibers that are slow twitch and fatigue resistant = most energy efficient

Question 5

Arches of the Foot

Answer 5

Passive Support:
4 layers of fibrous tissues: Plantar fascia (aponeurosis), long plantar ligament, short plantar ligament, spring ligament
Shape of articulating bones (talus as “keystone”)

Dynamic Support:
Longitudinal arch: Flexor hallucis longus, Flexor digitorum longus
Transverse arch: Tibialis anterior, Fibularis (peroneus) longus
Bracing action of intrinsic foot mm.

Question 6

Stride vs. Step

Answer 6

Stride: initial contact on one limb to the subsequent initial contact on the ipsilateral limb

Step: initial contact on one limb to the initial contact on the contralateral limb

Question 7

Stance and Swing Phases

Answer 7

Every stride has a stance phase when reference leg is touching the ground and then the swing phase when moving forward until heel comes down

Stance phase = heel strike to toe off
Swing phase = toe off to heel strike

Question 8

Gait Cycle Phases

Answer 8

During stance phase (1-5), the other leg is still on the ground creating a double support then swing phase (6-7) is single support then back to double support again
1. Heel strike (initial contact)
2. Loading response (foot flat)
3. Midstance
4. Terminal stance (heel off)
5. Pre-swing
6. Initial & Mid-swing
7. Terminal swing
1 is double support, 2-4 is single support, 5 is double support, and 6-7 is single support

Question 9

Vertical and Horizontal Forces

Answer 9

Heel on ground = negative horizontal force (deceleration from ground slowing you down) then positive acceleration phase when overcoming ground

Vertical Force (ground reaction forces/GRF) = during stance phase increases than decreases then increases, and then during swing phase decreases at toe off and force comes to 0

Question 10

Initial Contact/Heel Strike

Answer 10

Instantaneous event = Foot strikes the ground (“collision”)

Normal walking – heel strike
Beginning of support phase

Question 11

Loading Response

Answer 11

Duration: Body weight transferred from heel to whole foot (“flat foot”)
Shock absorption
Body weight is accepted onto supporting limb
Ankle plantarflexion with control to flatten foot (no “foot slap”)
Body weight passes forward over planted foot (mild knee flexion and beginning of hip extension)
Gait cycle’s 1st period of double limb support
Braking force (but COM continues forward by propulsive action of contralateral limb)

Question 12

Midstance

Answer 12

Duration: From beginning of single limb support until COM is directly over the supporting limb
1st half of single limb support
Increased load bearing
Preparation for propulsion!

Question 13

Terminal Stance

Answer 13

Heel Off and start to propel forward
Duration: COM over supporting foot to initial contact of contralateral foot
2nd half of single limb support
Center of gravity progresses beyond supporting foot (limb in trailing position)

Question 14

Pre-Swing

Answer 14

Duration: From onset of double limb support to toe off

Unloading limb
Weight transferred to contralateral limb in preparation for swing phase
Only the toe remains in contact with the ground

Question 15

Swing Phase

Answer 15

Duration: From toe off to heel strike
Advancement of limb
Foot clearance

From toe off when flexing during swing then knee goes from flexion to extension to get ready for heel strike /dorsiflexion
Hip is going through progressive flexion
Ankle goes from plantarflexion to dorsiflexion

Question 16

Mechanics of Locomotion

Answer 16

We move like an inverted pendulum
Weight is center of mass and lifts and falls
When you’re higher, the velocity is lowest and vice versa
Recover 70% of our energy by exchanging potential and kinetic energy on a FLAT surface
Choose relative walking speed to increase efficiency

Question 17

Muscle Activity Patterns for Support and Swing Phases

Answer 17

Support Phase: lesser gluteals and vastus medialis and lateralis are most active, and then triceps surae towards the end of the cycle

Swing Phase: Anterior tibial, satorius, and iliopsoas are most active

Question 18

Hip Extension

Answer 18

Hip extension resists further flexion due to forward momentum of torso during heel strike

Semimembranosus, semiteninosus, long head of biceps femoris, and gluteus maximus = all cross the hip joint to actively extend the leg at the hip joint
Short head of biceps femoris does not cross the hip joint and therefore is not involved

Question 19

Jack Knife Gait

Answer 19

Coming forward with heel strike so don’t fall forward
Heel strike and loading response see gluteus maximus and hamstrings, and if weakness = jack knife gait
Gluteal muscle keep from falling forward so lean back before heel strike to avoid falling forward = for gluteal lesions
Powerful movements usually use the gluteal muscles

Question 20

Quadriceps Gait

Answer 20

Femoral nerve injury

Patient doesn’t trust that the leg can control itself during stance phase and hand pushes the leg into extension to make sure the leg does extend = quads gait
Tendency for knee to collapse into flexion at initial contact and early loading response, so patient lurches body forward with upper limb assistance to keep knee extended
Quads are not used past the midstance phase

Question 21

Anterior Tibial and Triceps Surae Counteractions

Answer 21

Anterior tibial muscles resist plantarflexion at initial contact and loading response; swing phase dorsiflex

Triceps surae resists dorsiflexion at midstance phase; pre-swing phase plantarflexion

Question 22

Iliopsoas/Adductors and Anterior Tibial Muscles

Answer 22

Iliopsoas & Adductors: hip flexors to regulate degree of hip extension

Anterior tibial: active plantarflexion for propulsion

Question 23

Pre-Swing and Swing Phases

Answer 23

Swing phase to reposition foot for next phase and avoid foot drag and hip drop

Hamstrings: knee flexion then hip extensors to decelerate thigh
Iliopsoas and Sartorius: knee flexion then actively flex hip

Question 24

Steppage Gait

Answer 24

swing with greater hip and knee flexion, and no heel strike occurs with initial contact with forefoot

Question 25

Biological Springs

Answer 25

Plantar fascia: enough CT that can act like a spring

Spring elements within the muscle = titin

Question 26

Running

Answer 26

When we run, we do not use inverted pendulum to recover energy and use spring mechanics to recover energy. During running we load the limb and bend the knees and allow load to cause the springs to get stretched so we can recover the spring energy, and we have an aerial phase (no limbs on the ground)