Locomotor biomechanics

Question 1

List common lameness indications

Answer 1

• many described
• most commonly: walk/trot
• torso movement (head nod and hip/pelvic hike)
• limb movement (fetlock joint angle = relates to force, foot placement = crossing under body, swing phase movement = toe drag, step length, cranial/caudal phase)

Question 2

Outline head nod in relation to lameness

Answer 2

• drops on non-lame diagonal
• less excursion on lame diagonal
• accelerated upward on non-lame diagonal
• Force = movement * acceleration
• higher acceleration –> higher force

Question 3

Describe ‘hip hike’

Answer 3

hip on the lame side has a greater vertical displacement and appear to drop before hiking up to the original position

Question 4

Outline the mechanism for hip hike

Answer 4

• DURING LAME LIMB STANCE: small amount of force –> reduced fetlock hyperextension, small amount of rotation, reduced pushoff. Reduced pelvic movement.
• DURING SOUND LIMB STANCE: increased force –> more fetlock hyperextension, more rotation, increased pushoff. Increased pelvic movement more obvious on lame side
• overall pelvic rotation amplifies effect at level of tuber coxae
• same mechanism for TL lameness: increased force with sound limb, increased movement during sound limb stance, more obviously visible on contralateral side

Question 5

What is the most sensitive parameter for change in hip hike after blocking (nerve)?

Answer 5

HHD = hip hike difference

Question 6

Outline the mechanics of force on a circle

Answer 6

• inwardly directed force provides centripetal acceleration

- result is alingment of limbs with GRF

Question 7

What is joint torque?

Answer 7

• GRF creates joint moments
• to provide stable support, the GRF moments need to be counteracted by internal forces (mm/ tendon forces)
• increased movement arm –> increased internal force
• increased tendon force –> increased stress/strain –> increased risk of injury

Question 8

What 3 factors may influence the inside/outside force?

Answer 8

• weight support
• stride length
• lean angle

Question 9

What dictates amount of vertical force?

Answer 9

gravity (vertical force is produced when the limb is in contact with the ground)

Question 10

Describe vertical force in different stride lengths

Answer 10

• shorter stance/ longer swing –> higher force
• longer stride –> longer swing phase –> higher phose
• outside limb needs to produce higher force

Question 11

Why is the lame limb often seen easiet on inside of circle/ lungeing?

Answer 11

lower force but more acute angle on inside of circle