What is a classical sign of distal limb stay apparatus failure seen during weight-bearing?

What is a classical sign of distal limb stay apparatus failure seen during weight-bearing?

• A. The fetlock raises higher than normal during weight bearing.
• B. The fetlock cocks or drops toward the ground under weight bearing due to loss of suspensory support.
• C. The horse exhibits excessive knee flexion.
• D. The hoof becomes permanently fixed in extension.

Answer: (D)

The distal limb stay apparatus provides passive support to keep the limb extended and stable under weight by using the suspensory system and associated ligaments. When this support fails, the limb can lose its control over extension and, in weight bearing, the hoof can become locked in an extended position. This persistent extension is a classic sign because it shows a loss of the normal, adjustable resistance that the stay apparatus normally provides, leaving the leg stiff and unable to flex as weight is carried. Other signs, like the fetlock dropping or rising during loading, can occur with injuries to the suspensory apparatus, but the most distinctive and telling presentation of distal stay apparatus failure is a hoof that remains permanently fixed in extension under load.