📝 STANDARD DESCRIPTION:
Type: Compound HINGE joint (mainly flexion-extension).
Composed of 4 separate joint levels:
1. Tibio-tarsal (between tibia and talus) — MAIN movement happens here.
2. Proximal intertarsal
3. Distal intertarsal
4. Tarso-metatarsal
(Lower 3 levels are almost immovable.)
Ligaments:
- Medial & Lateral Collateral ligaments (long & short parts).
- Long Plantar Ligament (back of hock — runs from calcaneus to metatarsus). Common site of 'CURB'.
Tendons crossing hock:
- Achilles tendon → tuber calcanei.
- SDF wraps around tuber calcanei (cap).
- DDF passes around the medial side (sustentaculum tali).
📚 DETAILED DESCRIPTION:
HOCK / TARSAL JOINT
The hock is a complex region with multiple joint levels stacked on top of each other. Almost all movement happens at the topmost level; the lower 3 levels are nearly fused.
JOINT LEVELS (top to bottom):
1. Tibio-tarsal joint (= proper hock joint) — between cochlea of tibia and trochlea of talus. Hinge joint. ALL hock movement (flexion/extension) happens here.
2. Proximal intertarsal joint — between proximal and middle row. Tiny movement.
3. Distal intertarsal joint — between middle and distal row. Almost no movement.
4. Tarso-metatarsal joint — between distal tarsals and cannon. Almost no movement.
LIGAMENTS:
• Medial Collateral Ligament (long & short parts).
• Lateral Collateral Ligament (long & short parts).
• Long Plantar Ligament: Strong cord on the plantar (back) surface of the hock from calcaneus to metatarsus. Sprain of this ligament = 'CURB' in horses (visible bow-shaped swelling on back of hock).
• Short ligaments between tarsal bones.
SUSTENTACULUM TALI: A shelf-like projection of the calcaneus. The DDF tendon glides over it (medially). Friction here can cause tarsal sheath tenosynovitis = 'thoroughpin'.
SYNOVIAL POUCHES: Each joint level has its own synovial sac. The tibio-tarsal pouch (highest, largest) is the entry site for arthrocentesis.
BIG CLINICAL DISORDERS:
• Bog Spavin: Distension of tibio-tarsal joint capsule (soft swelling on dorso-medial hock).
• Bone Spavin: Osteoarthritis of the lower hock joints (distal intertarsal + tarso-metatarsal).
• Capped Hock: Bursitis over tuber calcanei.
• Curb: Long plantar ligament strain.
• Thoroughpin: Tarsal sheath swelling.
// COMPARATIVE ANALYSIS
| HORSE |
Hock disorders are the #1 cause of hindlimb lameness — bog spavin, bone spavin, curb. |
| DOG |
Hock fractures common in racing greyhounds. |
CLINICAL RELEVANCE
Capped hock, curb, bog/bone spavin — all are clinical conditions of the hock. Each has a specific anatomical structure as origin.
