Welcome to our new style Bitesize Canine Anatomy
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The crus is the region between the stifle and hock. In this region there are 2 main groups of muscles: craniolateral + caudal.
The Cranial Tibial muscle is found in the craniolateral muscle group of the canine crus (leg) and is an intrinsic muscle.
Intrinsic muscle = muscle origin + insertion are within the pelvic limb (hind limb).
The craniolateral group of muscles of the crus region are;
- Cranial Tibial (Tibialis Cranialis): superficial + easily palpable
- Long Digital Extensor (Extensor Digitorum Longus): partially covered by Fibularis Longus + Cranial Tibial muscles
- Fibularis (Peroneus) Longus: small triangular shaped muscle easily palpable
- Lateral Digital Extensor (Extensor Digitorum Lateralis)
- Extensor Digit I Longus
The tibia's extensor groove (sulcus extensorius) is a small notch that cuts into the lateral condyle of the tibia, as far as the articular surface.
The Long Digital Extensor muscle arises from the extensor fossa of the lateral femoral condyle and passes distally through this groove.
The Cranial Tibial muscle origin includes the lateral aspect of the extensor groove and it covers much of the Long Digital Extensor muscle.
Origin: It arises on the cranial portion of the articular margin of the lateral condyle of the tibia + on the laterally arched edge of the cranial border of the tibia.
From its origin the muscle passes to the craniomedial aspect of the crus and becomes a thin flat tendon, passing obliquely over the cranial aspect of the tarsus to the medial side. It then turns and continues to the plantar surface.
Insertion: The tendon of insertion attaches to the plantar surface of the base (proximal aspect) of metatarsals 1 + 2.
Crural Extensor Retinaculum
Below you can see the crural extensor retinaculum (brown) in the distal part of the tibia. This broad piece of fascia is a great design feature to retain the group of tendons in place and optimise their function.
Tarsal Extensor Retinaculum
The second more distal loop of fascia that creates the tarsal extensor retinaculum, retains the Long Digital Extensor tendons deep to it.
OneShot Inside K9HS video 001
Cranial Tibial Muscle Fibre Type
The Cranial Tibial muscle predominantly contains Type II fast twitch muscle fibres.
EMG studies evidence the Cranial Tibial's neuromuscular activation in the swing phase during walking and trotting. This supports the muscle recruitment pattern as a primary role of tarsal (hock) flexion.
Innervation of Cranial Tibial Muscle
The Cranial Tibial Muscle is innervated by the Common Fibular nerve which is also known as the Common Peroneal nerve.
This is divided into the Superficial and Deep fibular nerves.
Oneshot Inside K9HS video 005
Actions of Cranial Tibial Muscle
The Cranial Tibial muscle is a dedicated hock flexor (tarsal flexion).
It also contributes to rotating the paw laterally (so the plantar aspect of the paw faces medially) and works with the hock medial rotators as part of dynamic paw balance in the dog.
This in turn optimises forward (sagittal plane) balanced motion in the dog and facilitates hind paw balance and movements on turning, when making directional changes.
Clinical Tip: Hock injuries are very common and often missed, ensure you compare the left and right hock flexion using therapeutic palpation of the relevant musculoskeletal structures.
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