Equine Lameness NAVLE Guide: Grading, Diagnosis, and High-Yield Conditions

Equine lameness is tested on the NAVLE from two angles: the diagnostic process (grading, nerve blocks) and specific high-yield conditions (navicular, laminitis, OCD). The nerve block interpretation is the most-tested concept—understand the principle and the specific block locations cold.

AAEP Lameness Grading Scale

Diagnostic Nerve Blocks

The principle: anesthetize a specific structure or region → if lameness improves significantly (60–100%), the source of pain is in the blocked region. Always start distally and work proximally.

• Palmar digital (PD) block: desensitizes the caudal third of the foot including the navicular bone, navicular bursa, deep digital flexor tendon insertion, and caudal DIP joint. Most commonly positive in navicular syndrome.
• Abaxial sesamoid block: desensitizes the entire foot including the dorsal DIP joint. More complete than PD block alone.
• Low palmar (low 4-point) block: desensitizes the fetlock region and lower limb.
• High palmar (high 4-point) block: desensitizes structures above the fetlock including the pastern.
• Intraarticular blocks: coffin joint, fetlock joint, carpal joints—more specific to articular sources.

Navicular Syndrome (Podotrochlosis)

Degenerative condition of the navicular apparatus: distal sesamoid bone, navicular bursa, DDFT, and associated collateral ligaments. Most common in Quarter Horses and warmbloods. Signs: bilateral forelimb lameness (worse on hard ground), pointing when resting, short choppy stride, heel pain on hoof testers, positive PD nerve block.