NAVLE Equine Lameness and Diagnostics Questions and Answers — Questions and Answers
Question 1: A 10-year-old Warmblood used for dressage presents with a 2/5 left forelimb lameness that resolves by over 90% following a palmar digital nerve block. Which of the following is the MOST likely source of the horse's pain?
- Metacarpophalangeal (fetlock) joint
- Proximal suspensory ligament
- Navicular bursa (Correct answer)
- Distal check ligament
Correct answer: Navicular bursa
The palmar digital nerve (PDN) block desensitizes the palmar third of the foot. This includes the navicular bone, navicular bursa, deep digital flexor tendon within the hoof capsule, the sole, frog, and palmar aspects of the coffin joint. The fetlock joint, proximal suspensory ligament, and distal check ligament are all located proximal to the area desensitized by a PDN block and would not be affected.
Question 2: Which of the following imaging modalities is considered the gold standard for achieving a definitive diagnosis of a deep digital flexor tendon lesion within the equine hoof capsule?
- Radiography
- Nuclear Scintigraphy
- Magnetic Resonance Imaging (MRI) (Correct answer)
- Diagnostic Ultrasonography
Correct answer: Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI) is the gold standard for imaging soft tissues within the hoof capsule because it provides superior detail and is not impeded by the hoof wall. Radiography is best for bone, diagnostic ultrasound cannot effectively penetrate the hoof capsule to visualize all relevant structures, and nuclear scintigraphy identifies areas of increased bone metabolism ('hot spots') but lacks specific soft tissue detail.
Question 3: A veterinarian observes a horse trotting on a hard, flat surface and notes a consistent head nod. The lameness is not apparent at a walk but is easily seen at the trot. According to the American Association of Equine Practitioners (AAEP) Lameness Scale, what is the most appropriate grade?
- Grade 2
- Grade 3 (Correct answer)
- Grade 1
- Grade 4
Correct answer: Grade 3
The AAEP Lameness Scale defines a Grade 3 lameness as one that is consistently observable at a trot under all circumstances. Grade 2 lameness is difficult to observe at a trot in a straight line but is consistent under specific circumstances (e.g., circling). Grade 1 is difficult to observe, and Grade 4 is obvious at a walk. The description of a lameness not seen at a walk but consistently visible with a head nod at a trot fits Grade 3.
Question 4: A 12-year-old Quarter Horse presents with a chronic, progressive, bilateral forelimb lameness and a short, choppy gait. The owner notes the horse frequently points one foot forward while at rest. Hoof testers elicit pain over the central third of the frog. Which of the following is the most likely diagnosis?
- High ringbone (pastern arthritis)
- Acute laminitis
- Navicular syndrome (Correct answer)
- Suspensory ligament branch desmitis
Correct answer: Navicular syndrome
This clinical presentation is classic for navicular syndrome (podotrochleosis), which involves pathology of the navicular bone and associated soft tissues. Key signs include chronic bilateral forelimb lameness, pointing a foot to relieve heel pressure, and pain over the frog/heel region with hoof testers. Ringbone affects the pastern, laminitis often has a more acute onset with different hoof tester responses, and suspensory issues are typically located more proximally.
Question 5: A positive response to a distal limb flexion test in a horse is most useful for localizing pain to which general anatomical area?
- Metacarpophalangeal joint and structures distal to it (Correct answer)
- Carpus and proximal metacarpal region
- Stifle and tarsus
- Elbow and shoulder
Correct answer: Metacarpophalangeal joint and structures distal to it
The distal limb flexion test specifically applies pressure to the joints and associated soft tissues of the fetlock, pastern, and coffin joint. A positive response (an increase in lameness after the hold) suggests a pain source within this region. While not perfectly specific, it effectively rules out primary pain from more proximal structures like the carpus, stifle, or shoulder, which are not significantly stressed by this particular test.
Question 6: To perform a complete low four-point nerve block on a forelimb, a veterinarian must anesthetize the medial and lateral palmar nerves as well as which other two nerves?
- Medial and lateral cutaneous antebrachial nerves
- Medial and lateral palmar metacarpal nerves (Correct answer)
- Deep and superficial branches of the radial nerve
- Axillary and musculocutaneous nerves
Correct answer: Medial and lateral palmar metacarpal nerves
The low four-point block is designed to desensitize the entire fetlock and structures distal to it. This requires blocking the medial and lateral palmar nerves (which run down the back of the leg) and the medial and lateral palmar metacarpal nerves (which run alongside the splint bones and provide deep/dorsal sensation to the fetlock). The other nerve pairs listed are located much more proximally in the equine forelimb.
NAVLE Equine Lameness and Diagnostics Questions and Answers
A 10-year-old Warmblood used for dressage presents with a 2/5 left forelimb lameness that resolves by over 90% following a palmar digital nerve block.
Which of the following is the MOST likely source of the horse's pain?