Gross Anatomy
[an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive] [an error occurred while processing this directive]  
THE GAIT CYCLE

(The information contained in this presentation can also be found in the video The Anatomical Gait Cycle). Also, read pgs. 712 -714)

I. FUNCTIONS OF THE LOWER EXTREMITY

Bipedalism is the process by which we are able to stand upright and to move about on 2 limbs.

Bipedalism imparts three unique functions on the lower limbs. The limbs must

  • bear weight
  • provide a means for locomotion
  • maintain equilibrium.

The lower limbs are adapted for stability rather than range of motion and that stability is achieved at most of the major joints of the lower limb through the use of strong ligaments and tight fitting bony surfaces rather than the expenditure of energy in the form of muscle contraction.

  1. Weight Bearing Properties
    1. Support weight of head and torso with minimal expenditure of energy
    2. Bony Features
      1. Relatively large areas of articulation
      2. Close pack fit of articular surfaces of bones involved in the formation of joints
        1. Hip joint
      3. Wide surface areas
        1. Knee joint
      4. Weight supporting arches
        1. Arches of the foot
    3. Ligaments
      1. Strong
      2. Maintain stable configuration
  2. Center of Gravity
    1. Center of mass of body generally falls halfway between iliac crests and in front of second sacral vertebra
    2. Position
      1. Posterior to hip joint
      2. Anterior to knee joint
      3. Anterior to ankle joint
  3. Stability
    1. Position of joints during normal upright standing
      1. Due to center of mass of body
    2. Can be maintained while bearing weight with minimal expenditure of energy (muscle contraction)
    3. Stable position maintained through use of :
      1. ligaments
      2. close packing of joints
    4. Position
      1. Hip joint = extension
      2. Knee joint = extension
      3. Ankle joint = dorsiflexion
      4. no ligamentous support
      5. Foot = supinated position

II. Locomotion

  1. Position of the Lower Extremity
    1. Weight bearing / Fixed
      1. Motion occurs with foot fixed to ground
      2. Limb is in good position to support weight
    2. Non weight bearing / Free
      1. Foot is not in contact with the ground
      2. Limb is not in a position to support weight
    3. Same relative motion occurs in both position
      1. Different bones will move
  2. B. Movements of the Lower Extremity
    1. 1. Hip Joint
      1. Weight bearing - pelvis moves on femur
      2. Non weight bearing - femur moves on pelvis
      3. Types
        1. Flexion - Extension
        2. Abduction - Adduction
        3. Medial rotation - Lateral rotation
    2. Knee Joint
      1. Weight bearing - femur moves on tibia
      2. Non weight bearing - tibia moves on femur
      3. Types
        1. Flexion - Extension
        2. Medial rotation - Lateral rotation
    3. 3. Ankle Joint
      1. Weight bearing - tibia and fibula moves on foot
      2. Non weight bearing - foot moves on tibia and fibula
      3. Types
      4. Dorsiflexion - Plantar flexion
    4. Foot (Tarsal Joints)
      1. Pronation - Supination

III. The Gait Cycle

  1. Definition
    The rhythmic alternating movements of the 2 lower extremities which result in the forward movement of the body. Simply stated, it is the manner in which we walk.
  2. Phases ( Fig. 1)
    1. STANCE ( support) PHASE - Begins when the heel of the forward limb makes contact with the ground and ends when the toe of the same limb leaves the ground.
      1. Heel Strike - heel of forward / reference foot touches the ground
      2. Mid Stance - foot is flat on the ground and the weight of the body is directly over the supporting limb.
      3. Toe Off - Only the big toe of the forward / reference limb in contact with the ground.
    2. SWING ( unsupported ) PHASE - Begins when the foot is no longer in contact with the ground. The limb is free to move.
      1. Acceleration - the swinging limb catches up to and passes the torso
      2. Deceleration - forward movement of the limb is slowed down to position the foot for heel strike.
    3. DOUBLE SUPPORT - both limbs are in contact with the ground simultaneously .
    4. GAIT CYCLE - the activity that occurs between heel strike of one limb ( reference limb) and the subsequent heel strike of that same limb.
  3. Analysis of the Gait Cycle - Joint Position
    1. Heel Strike
      1. Ankle joint = is in a neutral position. That is, it is neither dorsiflexed nor plantar flexed
      2. Knee joint = flexed
        1. Weight of body behind knee
        2. Slight flexion helps absorb the impact of the foot contacting the ground from impact between
      3. Hip joint flexed
        1. lengthens limb in preparation for contact between heel and ground. Helps provide for proper placement of foot so that the heel make contract with the ground.
      4. Foot = supinated
    2. Midstance
      1. Ankle joint = dorsiflexed
      2. Knee joint = extended
        1. lengthens limb to help support weight of torso which is now directly over limb
      3. Hip joint = Neutral
      4. Foot = Slight pronation
    3. Toe Off
      1. Ankle joint = plantar flexed
        1. triceps surae ( superficial muscles in posterior compartment of leg) begin to contract strongly bringing the ankle joint into a plantar flexed position
      2. Knee joint = flexed
        1. contraction of the gastrocnemius muscle , one of thew triceps surae muscles, causes active flexion of the knee joint
        2. shorten limb to allow clearance from ground
      3. Hip joint = Extended
        1. Torso on the opposite side has moved forward of reference limb
      4. Foot = supinated
    4. Acceleration
      1. Ankle joint = neutral
      2. Knee joint = flexed
        1. shorten limb to maintain foot off of the ground
      3. Hip joint = flexed
        1. Limb catches up to and then passes the torso
      4. Foot = slight pronation
  4. D. Determinants of Position
    1. Active factors
      1. Muscle activity is responsible for determining the position of the joint
    2. Passive factors
      1. Position of the joint is determined by forces such as gravity or movement of the opposite side of the body

IV. MUSCLE ACTIVITY (Chart I)
The major muscle groups that are active at each of the various phases of the gait cycle and the joint (s) upon which they act are listed below. This information is also presented in the tape "The Anatomical Gait Cycle". As you proceed to study of each major joint of the Lower Extremity , you should be able to do the following:

  1. Know the position of each of the joints of the lower limb at each interval of the gait cycle and the factors responsible for this position.
  2. Determine the major muscle groups acting on the particular joint and know the function(s) / actions(s) of each muscle
  3. Determine if the muscle has an restraining effect ( eccentric contraction) or a propulsive effect ( concentric contraction).
  4. Know the innervation of each muscle or group of muscles.
  5. Understand how to determine how a nerve lesion would affect the movement and position of the particular joint during the gait cycle.

MUSCLE ACTIVITY DURING GAIT

INTERVAL JOINT POSITION MUSCLE ACTIVITY
Acceleration to Heel Strike Hip Flexed Gluteus Maximus

Hamstrings

Gluteus medius & minimus
Knee Flexed Quadriceps femoris
Ankle Neutral Anterior crural muscles
Heel Strike to Midstance Hip Neutral Gluteus medius & minimus
Knee Extended Quadriceps femoris
Ankle Dorsiflexed Gastrocnemius; soleus
Tarsal Inverted Tibialis anterior

Tibialis posterior
Midstance to Toe Off Hip Extended -
Knee Flexed Gastrocnemius
Ankle Plantar flexed Gastrocnemius; soleus
Tarsal Everted Fibularis longus

Fibularis brevis
Toe Off to Acceleration Hip Flexed Iliopsoas

Adductors longus, brevis, magnus
Knee Flexed Gastrocnemius
Ankle Neutral Anterior crural muscles
Tarsal Neutral -

V. OBJECTIVES

  1. Define "center of gravity " and know where this point lies with respect to the hip, knee and ankle joints.
  2. Understand the factors that enable the lower extremity to bear weight.
  3. Be able to determine the most stable configuration for the hip, knee and ankle joints
    1. Know the factors responsible for the maintenance of the stable configuration
  4. Be able to define " Gait Cycle" and know the major phases of the gait cycle and their subdivisions.
  5. Be able to understand the position of the hip, knee , ankle and tarsal joints t at each phase of the gait cycle .
    1. Understand the factors responsible for each position.
  6. Know which muscle(s) are acting on a given joint of the lower limb at each phase of the gait cycle.
    1. Understand whether the muscles are acting in a concentric or eccentric manner
    2. How the action of the muscle(s) affects the position and movement of each major joint
  7. Understand the effect(s) of nerve lesions will have on the gait cycle. Be able to determine the site of a particular lesion based upon the functional deficits produced.
[an error occurred while processing this directive]