What fibrous structure passively supports the fetlock joint?

• A. Suspensory ligament
• B. SDF
• C. DDF
• D. Common digital extensor

Answer: (A)

Passive stability of the fetlock is provided by a fibrous suspensory ligament. This structure runs along the palmar/plantar side of the cannon bone and attaches to the proximal sesamoid bones, acting like a suspender to keep the fetlock from overextending when the limb bears weight. Its role is passive—no muscle contraction needed—so it continuously supports the joint under load.

The other options are tendons that actively move the limb. The superficial and deep digital flexor tendons cross the fetlock to flex the joint during movement, providing dynamic support but not serving as the primary passive stabilizer. The common digital extensor extends the limb rather than suspending it.