http://upload.orthobullets.com/topic/7001/images/gait cycle.jpg
Overview
  • One gait cycle is measured from heel-strike to heel-strike 
    • consists of 
      • stance phase
        • period of time that the foot is on the ground
        • ~60% of one gait cycle is spent in stance
        • during stance, the leg accepts body weight and provides single limb support
      • swing phase
        • period of time that the foot is off the ground moving forward
        • ~40% of one gait cycle is spent in swing
        • the limb advances
  • Stride
    • is the distance between consecutive inital contacts of the same foot with the ground
  • Step
    • is the distance between initial contacts of the alternating feet
Stance Phase
  • Initial contact (heel strike)  
    • definition
      • occurs when foot contacts the ground
    • muscular contractions
      • hip extensors contract to stabilize the hip 
      • quadriceps contract eccentrically
      • tibialis anterior contracts eccentrically 
  • Loading response (initial double limb support)
    • marks the beginning of the initial double limb stance
    • definition
      • occurs after initial contact until elevation of opposite limb
      • bodyweight is transferred on to the supporting limb
    • muscular contractions
      • ankle dorsiflexors (tibialis anterior) contract eccentrically to control plantar flexion moment
      • quads contract to stabilize knee and counteract the flexion moment (about the knee)
  • Mid-stance (single limb support)
    • initial period of single leg support
    • definition
      • from elevation of opposite limb until both ankles are aligned in coronal plane
    • muscular contractions
      • hip extensors and quads undergo concentric contraction 
  • Terminal stance (single limb support)
    • definition
      • begins when the supporting heel rises from the ground and continues until the opposite heel touches the ground
    • muscular contractions
      • toe flexors and tibialis posterior contract and are the most active during this phase   
  • Pre-swing (second double limb support)
    • is the start of the second double limb stance in the gait cycle
    • definition
      • from initial contact of opposite limb to just prior to elevation of ipsilateral limb
    • muscular contractions
      • hip flexors contract to propel advancing limb
Swing Phase
  • Initial swing (toe off)  
    • start of single limb support for opposite limb
    • definition
      • from elevation of limb to point of maximal knee flexion
    • muscular contractions
      • hip flexors concentrically contract to advance the swinging leg
  • Mid-swing (foot clearance)
    • definition
      • following knee flexion to point where tibia is vertical
    • muscular contractions
      • ankle dorsiflexors contract to ensure foot clearance
  • Terminal swing (tibia vertical)
    • definition
      • from point where tibia is vertical to just prior to initial contact
    • muscular contractions
      • hamstring muscles decelerate forward motion of thigh
Variables Affected During Gait Cycle
  • Pelvic rotation
    • pelvis rotates 4 degrees medially (anteriorly) on swing side
      • lengthens the limb as it prepares to accept weight
  • Pelvic tilt
    • pelvis drops 4 degrees on swing side
      • lowers COG at midstance
  • Knee flexion in stance
    • early knee flexion (15 degrees) at heel strike 
      • lowers COG, decreasing energy expenditure
      • also absorbs shock of heel strike
  • Foot mechanisms
    • ankle plantar flexion at heel strike and first part of stance
  • Knee mechanisms
    • at midstance, the knee extends as the ankle plantar flexes and foot supinates
    • restores leg to original length
    • reduces fall of pelvis at opposite heel strike
  • Lateral displacement of pelvis
    • pelvis shifts over stance limb 
      • COG must lie over base of support (stance limb)
  • Center of gravity (COG)
    • in standing position is 5cm anterior to S2 vertebral body
    • vertical displacement
      • during gait cycle COG displaces vertically in a rhythmic pattern
        • the highest point is during midstance phase
        • lowest point occurs at the time of double limb support
    • horizontal displacement
      • COG displaces 5cm horizontally during adult male step
Muscle Activity
  • Figure showing muscle activity through different phases of gait cycle  
 

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Questions (3)

(OBQ12.237) Which phase of gait is affected most in a patient with quadriceps atrophy? Review Topic

QID:4597
1

Terminal swing

21%

(600/2892)

2

Preswing

5%

(136/2892)

3

Initial swing

19%

(563/2892)

4

Midstance

44%

(1280/2892)

5

Midswing

10%

(290/2892)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

Quadriceps weakness is most likely to affect the stance phase of the gait cycle, making midstance the correct answer.

During the normal stance phase of gait, the quadriceps contracts to prevent buckling of the knee. In a patient with quadriceps atrophy, the patient leans forward at the hip causing the center of gravity to fall anterior to the knee. This causes the knee to go into hyperextension. In contrast, weakness of the hamstrings or the hip flexors are most likely to affect the swing phase of gait by limiting limb advancement.

Lim et al. discuss the evaluation of the elderly patient with an abnormal gait. They urge the clinician to identify and treat the cause of the gait disturbance, if possible. Common treatable neurologic causes include normal pressure hydrocephalus, vitamin B12 deficiency, Parkinson's, alcoholism, and medication toxicity. Common treatable musculoskeletal causes include cervical myelopathy, spinal stenosis, and contractures.

Video V shows how gait is affected when there is a quadriceps deficiency.

Incorrect Answers:
Answers 1, 2, 3, 5: The quadriceps is largely silent during the swing phase of gait.

ILLUSTRATIONS:

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(OBQ10.123) Which of the following descriptions of muscle activity during normal gait is correct? Review Topic

QID:3217
1

Gastrocnemius-soleus contracts eccentrically during heel strike

24%

(413/1731)

2

Gastrocnemius-soleus contracts concentrically during heel strike

7%

(114/1731)

3

Gastrocnemius-soleus contracts concentrically during swing phase

2%

(41/1731)

4

Tibialis anterior contracts concentrically during toe-off

3%

(50/1731)

5

Tibialis anterior contracts eccentrically at heel strike

64%

(1104/1731)

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PREFERRED RESPONSE 5

One stride (heel strike to heel strike of one leg) of normal gait has been divided into the stance (62%) and swing (38%) phases. The stance phase is further divided into heel strike, foot flat, and toe off. Proper gait requires coordinated contraction of the leg muscles.

The tibialis anterior (TA) muscle fires eccentrically at heel strike to lower the foot to the ground, while the gasto-soleus (GS) complex is dormant. The TA then relaxes, while the GS eccentrically contracts as the body’s weight is transferred forward over the foot during foot-flat. As the foot propels the body forward during toe-off, the GS contracts concentrically, while the TA remains dormant. As swing commences, the TA then fires concentrically producing dorsiflexion to clear the foot over the ground while the GS relaxes. Certain conditions like cerebral palsy result in improper firing of the muscles during the gait cycle, resulting in altered gait mechanics.

Illustration A demonstrates the phases of the gait cycle.

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(OBQ06.222) The primary antagonist of the anterior tibial tendon is innervated by which of the following nerves? Review Topic

QID:233
1

Superficial peroneal nerve

58%

(764/1323)

2

Deep peroneal nerve

10%

(135/1323)

3

Tibial nerve

23%

(310/1323)

4

Posterior tibial nerve

8%

(105/1323)

5

Sural nerve

1%

(7/1323)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

The primary antagonist of the anterior tibial tendon is the peroneus longus, which is innervated by the superficial peroneal nerve.

The peroneus longus (PL) and tibialis anterior (TA) are antagonists to each other as the PL plantarflexes and everts, while the TA dorsiflexes and inverts the foot. The peroneus brevis (PB) and posterior tibialis (PT) are antagonists to each other.

The cited cadaveric study by Silver found that the plantarflexors of the ankle were six times as strong as the dorsiflexors.


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