Hock and Distal Limb Muscles

M.8R, W.3, L.8

Describe the tarsus/hock (bones its composed of, type of bones, the different rows and what they’re composed of)

• composed of tarsal bones

• Type

  • short bones

• Proximal row

  • Talus​

  • Calcaneus

• Middle row

  • Central & 4th TBs​

• Distal row

  • I, 2, 3 & 4 TBs​

  • 4th TB bridges middle and distal rows​

Which part of the tarsus/hock is palpable and what row is it in?

Calcaneus

• proximal row

List the species differences of the tarsus/hock in regards to the equine

• Distal Row

  • 1 & 2 fused

  • 3 very large

List the 4 joints of the tarsus/hock

• Tibio-tarsal joint (TT):​

  • Talus - tibia & fibula​

• Proximal intertarsal joint (PIT):​

  • Talus & calcaneus -​ Central & 4 Tbs​

• Distal intertarsal joint (DIT):​

  • Central – 1, 2 & 3 TBs​

• Tarso-metatarsal joint (TMT):​

  • 1,2,3 & 4 TBs - metatarsal bones​

Which joint of the tarsus has the most movement

Tibio-tarsal joint

How is the communication between the compartments of the tarsus/hock?

poor communication between compartments

which joint of the tarsus is palpable and at what anatomical aspects is it palpable

• Tibio-tarsal joint

  • Dorsomedial aspect​

  • Plantarolateral aspect​

  • Plantaromedial aspect ​

List the structures that provide stability for the tarus/hock

1. Collateral ligaments:​

2. Fibrocartilagenous reinforcement of joint capsule

3. Retinaculum​

4. Plantar ligament​

Where are the collateral ligaments of the tarus/hock located?

• Long: Tibia – metatarsal bone​

• Short: Bridge bone – bone​

How many centers of ossification do the bones of teh tarsus/hock have and list the exception

• All single center of ossification

  • Except calcaneus = 2​

List the distal hindlimb muscles

• Cranial tibial muscle​​

Describe the Cranial tibial muscle​ (origin, insertion, function, nerve supply)

• Origin

  • proximal tibia​

• Insertion

  • metatarsal bones (all species)​

• Insertion

  • medial aspect hock (horse) =​ Cunean tendon​

• Function

  • Hock flexion​

• Nerve Supply

  • Peroneal / Fibular Nerve (branch of Sciatic)​

Describe the

• Origin

  • lateral tibia & fibula

• Insertion

  • Plantar aspect tarsus

• Function

  • Hock flexion​

• Nerve Supply

  • Peroneal / Fibular Nerve (branch of Sciatic)​

• Origin

  • lateral femoral condyle ​

    (with long digital extensor muscle)​

• Insertion

  • 3rd MT (with cranial tibial muscle)

• Insertion

  • lateral aspect tarsus

• Function

  • Hock flexion​

• Nerve Supply

  • Peroneal / Fibular Nerve (branch of Sciatic)​

Long Digital Extensor Muscle

• Origin

  • extensor fossa (femur)​

• Tendon of Origin

  • incorporated into stifle capsule

  • provides lateral collateral support to stifle

• Insertion

  • all digits ​

  • distal phalanx - extensor process​

• Function

  • Hock flexion​

  • Digital extension

• Nerve Supply

  • Peroneal / Fibular Nerve (branch of Sciatic)​

list the distal hindlimb muscles (caudal aspect of limb)

• Common calcanean tendon

Describe the Common Calcanean tendon

Components:​

1. Biceps femoris​

2. Semitendinosis​

3. Gracilis​

4. Gastrocnemius​

5. Superficial digital flexor​

• I – calcaneus ​

• Tuber calcis / calcanean tuberosity​

• Acts as lever for distal limb​

• Plantar ligament​

• Function

  • hock extension​

• Nerve supply

  • reflects contributors​

  • mixed nerve supply

  • mostly sciatic and tibial nerves contributing

Gastrocnemius muscle

• Origin

  • femur

• Insertion

  • calcaneous

• Function

  • hock extensor

  • stifle flexor

• Nerve supply

  • Tibial Nerve (branch of Sciatic)

Describe the Superficial Digital Flexor Muscle (Origin, Insertion, Function and Nerve Supply)

• Origin

  • distal femur

• Insertion

  • calcaneus

• Insertion

  • branches to all digits (middle phalanx)

• Function

  • hock extension

  • digital flexion

• Nerve supply

  • Tibial Nerve (branch of Sciatic)

Describe the Deep Digital Flexor Muscle (origin, insertion, function, and nerve supply)

• Origin

  • Tibia

• Insertion

  • branches to all digits (middle phalanx)

• Function

  • hock extensor

  • digital flexor

• Nerve Supply

  • Tibial Nerve (branch of Sciatic)

What is the natural weightbearing position of the hindlimb stay apparatus?

Extension

What do the MTP, PIP and DIP joints prevent?

hyperextension

List the muscles that create a combined force for hindlimb extension

• Gluteal muscles

• hip extensors / limb retractors

• stifle extensors

• hock extensors

Where are the forces of the muscles during hindlimb extension directed?

caudally in axial plane