NAVLE Musculoskeletal

Equine Flexural Deformities Study Guide

Flexural limb deformities (FLDs) are deviations in the sagittal plane characterized by abnormal flexion or extension of joints.

Overview and Clinical Importance

Flexural limb deformities (FLDs) are deviations in the sagittal plane characterized by abnormal flexion or extension of joints. These conditions are frequently encountered in equine practice, particularly in neonatal foals and rapidly growing young horses. FLDs represent a significant category of developmental orthopedic disease on the NAVLE and require thorough understanding of anatomy, pathophysiology, and treatment options.

FLDs are divided into two main categories: contractural deformities (hyperflexion, commonly called "contracted tendons") and hyperextension deformities (flexor tendon laxity). Both types can be congenital (present at birth) or acquired (developing later in life).

High-YieldThe term "contracted tendons" is a misnomer. The tendons themselves do not contract; rather, there is a mismatch between the length of the musculotendinous unit and the bone, or shortening of the muscle-tendon-ligament complex.
Classification Joint Affected Structure Involved Typical Age at Onset
DIP Joint Contracture (Club Foot) Distal interphalangeal joint (coffin joint) DDFT musculotendinous unit Congenital or 2-6 months (acquired)
MCP/MTP Contracture (Fetlock) Metacarpophalangeal or metatarsophalangeal joint SDFT and/or DDFT Congenital or 9-18 months (acquired)
Carpal Contracture Carpus (knee) Joint capsule, ulnaris lateralis, flexor carpi ulnaris Usually congenital or 1-6 months
Hyperextension (Laxity) Fetlock, pastern, or carpus Flexor tendons (weak/lax) Neonates (especially premature)

Anatomy Review

Understanding the anatomy of the equine distal limb is essential for diagnosing and treating flexural deformities. The key structures include:

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