Name two alternative causes of hind limb lameness that may mimic PSD in horses.

Name two alternative causes of hind limb lameness that may mimic PSD in horses.

• A. Carpal bone fracture and radial nerve injury.
• B. Proximal sesamoid bone injury and collateral ligament injuries.
• C. Hoof abscess and navicular syndrome.
• D. Muscle strain of the gluteal region.

Answer: (B)

Horses showing hind limb lameness that localizes around the fetlock can be caused by problems in structures that support or surround the suspensory apparatus, not just the proximal suspensory ligament itself. Proximal sesamoid bone injuries sit at the base of the suspensory system and disrupt the same region that PSD affects. This can produce fetlock pain, lameness that worsens under load, and a positive provocative exam, making it easy to mistake for PSD without targeted imaging. Collateral ligament injuries of the fetlock are another close mimic; damage to the medial or lateral ligaments causes pain and instability in the same joint area, yielding a similar gait pattern and response to examination maneuvers. Imaging helps distinguish these from true PSD: radiographs or CT can reveal proximal sesamoid bone damage, while ultrasound or MRI can show collateral ligament compromise. The other options involve regions or conditions that either aren’t primarily hind limb fetlock problems or don’t typically present with the same regional signs, so they’re less likely to be mistaken for PSD.