Page 315 - Canine Lameness

18.2 ­ormal Anatomy 287

(A) (B) (C) (D)

Figure 18.3 Ligaments of the tarsal joint: (A) medial aspect illustrating the (a) medial long collateral and TARSAL REGION
the (b, c) medial short collateral complex which includes the (b) tibiotalar short collateral and (c) tibiocentral
short collateral; (B) lateral aspect illustrating the (d) lateral long collateral, (e) calcaneoquartal ligament and
the (f, g) lateral short collateral complex which includes the (f) calcaneofibular short collateral, and (g)
talofibular short collateral; (C) plantar aspect illustrating the (h) long plantar ligament, (i) calcaneocentral
ligament, (j) plantar centrodistal ligament, and (k) tarsal fibrocartilage; and (D) dorsal aspect illustrating the
(l) crural extensor retinaculum.

component that runs from the appropriate malleolus to the base of metatarsals I and II on the
medial side and V on the lateral side, attaching to each tarsal bone the ligament passes on the way
(Figure 18.3). This long component is taut when the tarsocrural joint is extended. On both sides,
there are two short components located deep to the long component (Aron and Purinton 1985);
these are taut when the tarsocrural joint is flexed. As most dogs walk with a few degrees of valgus
angulation that places tensile stress on the medial aspect of the tarsus, medial collateral injuries
are more likely to result in persistent lameness than lateral collateral injuries (Decamp et al. 2016).
The tarsocrural joint flexes to varying degrees during gait, but the rest of the tarsus remains
straight because of the support provided by the strong plantar ligaments. The middle (or long) plan-
tar ligament originates on the body of the calcaneus and attaches to the fourth tarsal bone before
inserting on the fourth and fifth metatarsal bones. The medial plantar ligament runs from the sus-
tentaculum tali to the central tarsal bone to attach to the first through third metatarsal bones. Before
reaching their metatarsal insertions, both of these ligaments attach to a thickened portion of the
joint capsule called the tarsal fibrocartilage. The lateral (or calcaneoquartal) plantar ligament origi-
nates on the plantarolateral surface of the calcaneal body and joins the long part of the lateral col-
lateral ligament before inserting on the fifth metatarsal bone (Carmichael and Marshall 2018).
Dorsal support of the tarsus is provided by a slender band running from the crural extensor reti-
naculum to the talus, where it joins with a shorter, denser ligament (the dorsal centrodistal) run-
ning from the talar neck to the second, third, and fourth tarsal bones. This ligament system, along
with the action of the fibularis and cranial tibial tendons, helps to limit tarsal extension.