📝 STANDARD DESCRIPTION:
Type: Intrinsic, Forearm (Flexor Group)
Heads: Humeral (medial epicondyle), Radial (caudal radius), Ulnar (caudal ulna)
Insertion: Flexor tubercle of Distal Phalanx (P3/coffin bone) of Digits III & IV
Function: Flexes distal phalanx (coffin joint) and all proximal joints.
📚 DETAILED DESCRIPTION:
THE ULTIMATE DIGITAL FLEXOR
The powerhouse of digital flexion, originating from three heads and terminating on the coffin bone.
TRI-HEADED COMPLEXITY:
• Humeral Head: Largest; from medial epicondyle
• Radial Head: From caudal surface of radius
• Ulnar Head: From caudal surface of ulna
The three heads fuse proximal to the carpus into a single massive tendon.
CARPAL CANAL PASSAGE: Passes through the carpal canal deep to the SDF tendon—the most dorsal structure in the flexor group at the carpus, most palmar at the digit.
DISTAL COURSE: Single massive tendon passes to fetlock, then splits into two tendons (one per digit), each passing through the manica flexoria of the SDF, then continuing to insert on the flexor tubercle of P3 (coffin bone/distal phalanx).
FUNCTIONAL ROLE: Flexes the coffin joint (DIP) primarily, but due to its passage through the fetlock and pastern regions, it secondarily flexes all proximal joints. Essential for gripping and traction.
// COMPARATIVE ANALYSIS
| HORSE |
Three heads (humeral, radial, ulnar); massive DDF tendon. |
| DOG |
Variable presence of radial head. |
CLINICAL RELEVANCE
Ascending Tenosynovitis: Puncture wounds to sole can infect digital sheath, leading to life-threatening ascending infection. Deep Flexor Tendonitis: 'Sole bruising' often reflects DDF stress.
