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Tarsus Anatomy
Dane Tatarniuk, DVM
Bones
• Talus b.• Calcaneus b.• Central tarsal b.• 1st & 2nd (fused) tarsal b.• 3rd tarsal b.• 4th tarsal b.
• Proximally: Tibia• Distally: 2nd, 3rd, 4th metatarsal b.
Dorsal-Plantar Lateral-medial
DLPMO DMPLO
PMDLO PLDMO
Plantar-Dorsal
Joints
• Tarsocrural• Talocalcaneal• Proximal Intertarsal• Talocalcaneal-Centroquatral
• Distal Intertarsal– Centrodistal
• Tarsometatarsal
Tarsocrural
• Ginglymus Joint– Hinge-like joint, direction in only one plane– Deep grooves in cochlear surface of distal tibia,
and trochlea of the talus• Articulation– 12 to 15 degrees to the sagittal plane, in dorsal-
lateral direction
PIT / DIT / TMT
• Plane joints• Only a very limited gliding movement
Joint Capsule
• Proximal: attaches to distal aspect of the tibia• Distal: attaches to metatarsal bones• Joint Pouch Effusion:– Dorsal-medial aspect of joint capsule, at level of
medial trochlea– Proximal aspect of plantar joint capsule, at level of
talus and distal tibia, both medial/lateral side
Ligaments
• Lateral Long Collateral Ligament– Superficial– Originate: Caudal aspect of lateral malleolus of
distal tibia– Inserts: Fourth tarsal b., third metatarsal b., fourth
metatarsal b.– Forms canal for lateral digital extensor tendon
Ligaments
• Lateral Short Collateral Ligament– Deep to long collateral– Originates: Cranial aspect of lateral malleolus of
the distal tibia– Runs caudally– Insertion: Lateral aspect of calcaneus
Ligaments
• Medial Long Collateral Ligament– Originates: Caudal aspect of medial malleolus of
distal tibia– Insertion: Second metatarsal b., third metatarsal
b., medial aspect third tarsal b.
Ligaments
• Medial Short Collateral Ligament– Deep to medial long collateral– Originates: Cranial aspect of the medial malleolus
of distal tibia– Insertion: Medial aspect of the calcaneus and
sustentaculum tali
Ligaments
• Long Plantar Ligament – Strong, flat band– Originates: Proximal plantar aspect of calcaneus– Insertion: Fourth metatarsal b., fourth tarsal b.
Ligaments
• Dorsal tarsal ligament– Originates: Distal tuberosity of the talus– Insertion: Central tarsal b., third tarsal b., proximal
third metatarsal b.
Muscle/Tendons
• Cranial-lateral– Tibialis cranialis• Flexor of hock• Originates from lateral condyle of tibia• Tendon passes through split in peroneus tertius• Tibialis cranialis tendon then splits itself• Insertion:
– Dorsal branch, proximal third metatarsus– Medial branch, crosses the medial long collateral ligament and
inserts on the fused 1st & 2nd tarsal bone
• Innervated by peroneal nerve
Muscle/Tendons
• Cranial-lateral– Peroneus tertius• Originates from distal femur• Courses alongside the long extensor muscle• Bifurcates at the dorsal tarsus• Lateral branch inserts on calcaneous b. and fourth
tarsal b.• Dorsal branch inserts on the proximal third metatarsal• Links the flexion of hock and stifle• Innervated by peroneal nerve
Muscle/Tendons
• Cranial-lateral– Long digital extensor• Originates from distal femur• Inserts on the extensor process of third phalanx• Lateral extensor tendon joins into long at level of
proximal metatarsus• Tendon sheath present as it crosses the dorsal tarsus• Held in place by 3 retinacula• Synovial sheath present• Flexes the hock, extends the digit• Innervated by peroneal nerve
Muscle/Tendons
• Cranial-lateral– Lateral digital extensor
• Originates lateral collateral ligament of stifle• Inserts (joins) into the long extensor tendon• Held in place by retinaculum• Synovial sheath present• Innervated by peroneal nerve
– Extensor digitalis brevis• Small, short digital extensor tendon between the angle of
the long and lateral digital extensor tendons
Muscle/Tendons
• Caudal– Gastrocnemius• Originates from 2 heads on the supracondylar
tuberosities of the femur, superficial to SDFT• Inserts on the points of the calcaneus, deep to
superficial digital flexor tendon• Extends the hock• Innervated by tibial nerve
Muscle/Tendons
• Caudal– Superficial digital flexor• Originates from the supracondylar fossa of femur, deep
to gastrocnemius• Twists medially to become superficial to gastrocnemius• Medial and lateral aspects insert on the point of the
calcaneus• Remainder of SDFT continues down plantar aspect of
distal limb, inserts on first and second phalanx• Innervated by tibial nerve
Muscle/Tendons
• Caudal– Deep digital flexor tendon
• Originates from three heads– Lateral digital flexor & Tibialis caudalis
» Originates from caudal tibia» Become joined, pass through the sustentaculum tali» Tarsal sheath
– Medial digital flexor» Originates from lateral condyle of tibia» Passes within groove on medial malleolus and medial
collateral ligament
• Innervated by tibial nerve
Tendon Sheaths
• All the tendons coursing over the hock, with exception of superficial digital flexor tendon, have a concurrent tendon sheath
Bursas
• Cunean Bursa– Directly deep to the
cunean tendon• Calcaneal Bursa (2)– Subcutaneous– Subtendinous
Nerves & Vessels
Nerves & Vessels
References• Dr. Alexander zur Linden, http://vetmed.iastate.edu/limbanatomy/horse.html• Horowitz A., Berg R., “Anatomy of the Horse”, 5th ed.• Moyer, “Equine Joint Injection and Regional Anesthesia”, 3rd ed.