Flashcards in Locomotor biomechanics Deck (11)
List common lameness indications
- 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)
Outline head nod in relation to lameness
- drops on non-lame diagonal
- less excursion on lame diagonal
- accelerated upward on non-lame diagonal
- Force = movement * acceleration
- higher acceleration --> higher force
Describe 'hip hike'
hip on the lame side has a greater vertical displacement and appear to drop before hiking up to the original position
Outline the mechanism for hip hike
- 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
What is the most sensitive parameter for change in hip hike after blocking (nerve)?
HHD = hip hike difference
Outline the mechanics of force on a circle
- inwardly directed force provides centripetal acceleration
- result is alingment of limbs with GRF
What is joint torque?
- 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
What 3 factors may influence the inside/outside force?
- weight support
- stride length
- lean angle
What dictates amount of vertical force?
gravity (vertical force is produced when the limb is in contact with the ground)
Describe vertical force in different stride lengths
- shorter stance/ longer swing --> higher force
- longer stride --> longer swing phase --> higher phose
- outside limb needs to produce higher force