Page 322 - Canine Lameness

294 18 Tarsal Region

of the metatarsus to stress the lower part of the tarsus in flexion (Figure 18.5). Dorsal angula -
tion will be evident at the level of instability. And vice versa, for detection of dorsal ligament
instability, the pressure to the distal pes would be applied in a plantar fashion during extension
of the tarsal joint.

18.5 Pathology of the Common Calcanean Tendon

The CCT (also referred to as “Achilles tendon”) includes all structures that attach to the tuber cal-
canei. It is formed by the (i) GT, (ii) the SDFT, (iii) and the conjoined tendon (also referred to as
TARSAL REGION “accessory” or “combined” tendon) of the following three muscles: biceps femoris, gracilis, and
semitendinosus. The gastrocnemius muscle originates from the distal, caudal femur and forms the
GT approximately at the level of mid-tibia. This tendon is the main component of the CCT and the
major muscle responsible for tarsal extension. The superficial digital flexor (SDF) muscle origi-
nates together with the lateral head of the gastrocnemius muscle on the distal, caudal femur and
continues cranially to the gastrocnemius muscle proximally but then the SDFT wraps around the
GT medially to become the most caudal attachment to the tuber calcanei (Figure 18.7). This attach-
ment is accomplished by a broad, fibrocartilaginous “caplike”-structure attaching collaterally to
the calcaneus, which allows the SDFT to continue distally to its distal attachment at the plantar
surface of the proximal base of phalanges II–V, thereby providing stifle flexion, tarsal extension,

(A) (B) (C)

Figure 18.7 Type IIc Achilles tendinopathy: (A) the (a) gastrocnemius tendon is (red arrow) partially
disrupted, resulting in slight hyperflexion (plantigrade) stance. Since the (b) superficial digital flexor tendon
is (blue arrow) intact, the increased flexion angle forces the digits into (black arrow) flexion, which results in
the typical “crab-claw” stance. (B, C) The superficial digital flexor tendon wraps around the gastrocnemius
tendon medially to form a cap that attaches caudally to the tuber calcanei. When palpating the tendons
above the calcaneus, isolation of the tendons is possible if the tendons are not affected by pathology.