1.0 Subjective Investigation of the Lame Horse

Question 1

What are the main steps in approaching the lame horse?

Answer 1

(1) history

• signalment (sex, breed, age, use)
• current problem: trauma?, duration, trajectory, effects of exercise/rest, changes to lifestyle
• past problems: recurring, or isolated? (also important for insurance reasons)
• type of sporting activity: level of competition
• additional sources: video, past diagnostic imaging, etc.

(2) stationary observation

• symmetry
• posture
• conformation

(3) palpation and hoof testers

• hoof testers: useful when assessing the presence of hoof abcesses
• flexor tendons: palpate under laoded and unloaded conditions (also feel insertions)
• joints: distention, temperature, pain, ROM
• back and pelvis: tuber coxae and tuber ischii
• easiest to work from distal to proximal

(4) gait observation / movement

• trot most useful: straight line, lunge (hard and soft surfaces)
• goal is to locate source of lameness for targeted diagnostic imaging
• limb movement is composed of travel and action

(5) further tests

• flexion tests and other manipulations
• diagnostic analgesia: nerve and joint blocks
• diagnostic imaging

Question 2

What is travel and action?

Answer 2

they are the two components of limb movement

travel is the flight of a single hoof in relation to other limbs

• often viewed from the side or from behind
• unusual travel does not necessarily indicate lameness

action is the overall description of gait characteristics

• takes into account joint flexion, stride length, suspension, etc.
• variation between different types and breeds

Question 3

What are the phases of natural hoof movement?

Answer 3

think of it as a clock with the hoof as the center, and fetlock as the hour hand; the ground is at the diameter of the clock, bisecting it from 9 to 3 o’clock

1. landing (fetlock at 10 o’clock)
2. loading (fetlock sinks nearly to 9 o’clock)
3. stance (fetlock springs up toward 11 o’clock)
4. breakover (the action of moving from 11-12-1-2 o’clock)
5. swing (~3 when hoof tip leaves ground)

Question 4

What are the natural gaits of the horse?

And which is best for identifying lameness?

Answer 4

(1) walk

• even rhythm four-beat gait
• not very suitable to recognize subtle lameness

(2) pace

• two-beat lateral gait (ipsilateral forelimb and hindlimbs elevate alternatively
• viable gait for standardbred (STB) racehorses but considered an impure gait for most “normal” horses

(3) trot

• two-beat diagonal gait
• steadiest and most rhythmic gait
• trot is great for evaluating lameness (most of all analyses are done via a trot)

(4) canter

• three-beat gait with lead preference
• difficult to identify subtle lameness but useful for back/rider/saddle associated problems

note: treadmills also are a great tool: offer standardized view that the outdoors cannot

Question 5

What is the subjective quantification of lameness?

Answer 5

Grade 0: sound

Grade 2/10: lameness hard to detect at walk or trot

Grade 4/10: lameness barely detectable at walk, easy to see at trot

Grade 6/10: lameness easily detectable at walk

Grade 8/10: hobbling at walk; unable/unwilling to trot

Grade 10/10: non weight-bearing

note: not an absolute scale, just be consistent about how you grade

Question 6

How do you recognize lameness in the horse?

Answer 6

(1) from the side

• “fetlock drop” (extension) more pronounced on sound side (increased loading), EXCEPT with tendon or suspensory ligament damage
• change in limb flight characteristics (cranial and caudal phases of stride)

(2) forelimb lameness

• cardinal sign = nead hike: head elevation on lame side because RAISING the head reduces the load on the unsound forelimb
• note, also can be seen as head nod or dip on sound side
• asymmetrical contraction of the pectoral muscle
• sound/concussion quieter on lame limb (less landing pressure)

(3) hindlimb lameness

• pelvic hike: hips raise on lame side (reduced pressure)
• greater excersion of tuber coxae (distance b/w highest and lowest point) on lame limb
• elevation of tuber calcis (hock) on sound side
• sound quieter on lame side
• drifting: horse moves AWAY from LAME limb (inconsistent feature but note if present)

Question 7

What are inertial sensor measurements?

Answer 7

small, lightweight and easily attached sensors that allow experts to quantify back movement parameters as well as the ‘traditional’ lameness parameters

enables one to construct a precise analysis of the interactions between different anatomical parts in lame horses, even almost imperceptible asymmetries

• in forelimb lameness: see decreased stance phase on the lame limb
• in hindlimb lameness: elevated pelvic height on lame side due to a reduction in loading