NAVLE Equine Lameness and Diagnostics 2 — Questions and Answers
Question 1: A horse presents with a positive flexion test of the distal limb and lameness that is abolished by a palmar digital nerve block. Which structure is MOST likely affected?
- Navicular bone or navicular bursa (Correct answer)
- Coffin joint
- Pastern joint
- Digital flexor tendon sheath
Correct answer: Navicular bone or navicular bursa
A palmar digital nerve block desensitizes the navicular region, and a positive distal limb flexion test implicates the navicular apparatus as the primary source of pain.
Question 2: Which radiographic view is MOST useful for evaluating the flexor cortex of the navicular bone for lollipop lesions in a horse?
- Lateromedial view
- Dorsopalmar view
- Flexor tangential (skyline) view (Correct answer)
- Oblique view
Correct answer: Flexor tangential (skyline) view
The flexor tangential (skyline) view projects the flexor cortex of the navicular bone en face, allowing visualization of corticomedullary defects and lollipop lesions.
Question 3: A 10-year-old Warmblood shows grade 3/5 forelimb lameness that worsens on the lunge circle with the affected limb on the inside. Lameness is abolished by an abaxial sesamoid nerve block. The NEXT most appropriate diagnostic step is:
- MRI of the foot
- Low 4-point nerve block
- Intra-articular anesthesia of the fetlock joint (Correct answer)
- Radiographs of the pastern
Correct answer: Intra-articular anesthesia of the fetlock joint
After an abaxial sesamoid block confirms pain distal to the fetlock, intra-articular anesthesia of the fetlock joint helps differentiate fetlock joint pathology from other sources in that region.
Question 4: Osteochondrosis dissecans (OCD) in horses most commonly affects which joint when presenting as tarsal lameness in young Thoroughbreds?
- Proximal interphalangeal (pastern) joint
- Distal intertarsal joint
- Tarsometatarsal joint
- Tarsocrural (tibiotarsal) joint (Correct answer)
Correct answer: Tarsocrural (tibiotarsal) joint
OCD most commonly affects the tarsocrural joint in horses, particularly the distal intermediate ridge of the tibia and the lateral trochlear ridge of the talus.
Question 5: When performing a high plantar nerve block (high 2-point block) in the horse, the targeted nerves are located:
- Just proximal to the fetlock, medial and lateral to the flexor tendons
- At the level of the proximal sesamoid bones
- Midway up the cannon bone, abaxial to the suspensory ligament (Correct answer)
- At the level of the tarsus, caudal to the saphenous vein
Correct answer: Midway up the cannon bone, abaxial to the suspensory ligament
The high plantar (high 2-point) block is performed midway up the cannon bone, anesthetizing the medial and lateral plantar nerves abaxial to the suspensory ligament.
Question 6: A horse has progressive weight-bearing lameness and perineural anesthesia of the ulnar and median nerves abolishes the lameness. Which region is MOST likely the source of pain?
- Foot and pastern region
- Fetlock joint
- Carpus and distal forelimb (Correct answer)
- Elbow joint
Correct answer: Carpus and distal forelimb
Median and ulnar nerve blocks desensitize the carpal region and distal limb below the elbow, so abolition of lameness localizes pain to the carpus or below.
Question 7: Nuclear scintigraphy (bone scan) in equine lameness is particularly valuable for identifying:
- Soft tissue injuries with low bone involvement
- Areas of increased bone remodeling before radiographic changes appear (Correct answer)
- Joint effusion and synovial inflammation
- Nerve compression along the digital sheath
Correct answer: Areas of increased bone remodeling before radiographic changes appear
Bone scintigraphy detects areas of increased osteoblastic activity and bone remodeling that may precede visible radiographic changes, making it useful for early stress fractures and occult bone pain.
NAVLE Equine Lameness and Diagnostics 2
A horse presents with a positive flexion test of the distal limb and lameness that is abolished by a palmar digital nerve block.
Which structure is MOST likely affected?