- The bones that make up the lower leg are the Cannon bone, Splint Bones, Long Pastern, Short Pastern, Pedal Bone and Navicular Bone.
- The tendons of the lower leg are the Deep Digital Flexor Tendon, Superficial Digital Flexor Tendon, Lateral Digital Flexor Tendon and Common Digital Flexor Tendon.
- Internal structures of the lower leg are the Navicular Bursa and the Digital Cushion.
- External structures are the Hoof Wall, Heel, Bars, Sole, Periople, Coronary band and Periople.
- Ligaments of the lower limb are Suspensory Ligament, Inferior Check Ligament, Superior Check Ligament, Annular Ligament, Interosseous Ligament, Impar Ligament, Proximal and Distal Check Ligaments.
- Sensitive structures of the hoof are the White Line and the Sensitive and Horny Laminae.
Bones of the Lower leg
- Cannon Bone
This is also called the 3rd Metacarpal and has the Splint bones running down either side of it
- Long Pastern
This is also called the First phalanx and leads onto the short pastern at the hoof end and the cannon bone at the other.
- Short pastern Bone
This is also known as the Second Phalanx and is situated just above the hoof wall and below the fetlock to form one of the lower limb bones. The short pastern follows on to the long pastern going up the lower limb and to the coffin bone going down the limb and it aids the horse in supporting weight.
- Pedal Bone
This is also called the distal, third Phalanx or coffin bone is situated in the hoof wall leading on to the Short pastern bone and aids the horse in supporting its weight. It is to the Pedal Bone that the Deep Digital Flexor Tendon attaches.
- Navicular Bone
Also called the distal sesamoid bone and is positioned at the back of the pedal bone and short pastern. It is from the navicular bone that the deep digital flexor tendon passes around before attaching itself to the pedal bone.
- Splint bone
On either side of the Canon bone are two smaller bones called Splint bones, they are wide at the top of the Canon bone and get progressively thinner as they run down to just below the halfway point of the canon bone. The Splint bone on the outside of the canon bone is called the Lateral Splint Bone or 4th Metacarpal and the Splint bone on the inside is called the Medial Splint Bone or 2nd Metacarpal
Ligaments Of The Lower Limb
Ligaments are bands of fibrous tissue that join bone to bone.
- Suspensory Ligament
This originates from between below the knee at the Canon bone where it runs down the Splint Bones to the Fetlock and splits into two branches each branch going to the Sesamoid Bone at the back of the Fetlock helping to support the joint before continuing down and attaching to the extensor tendons.
- Inferior Check Ligament
Originates at the back of the knee where it supports the Deep Digital Flexor Tendon.
- Annular Ligament
This is formed where the Superficial Flexor Tendon covers the Deep Digital Flexor Tendon and sheath at the back of the Fetlock joint before attaching itself to the Sesamoid Bones.
- Inter osseous Ligaments
These act to connect the Splint Bone to the Canon Bone.
- Impar Ligament
This joins the Pedal Bone and the Navicular Bone together.
- Proximal Check Ligament
This originates at the Radius and attaches itself to the Superficial Digital Flexor Tendon.
- Distal Check Ligaments
This originates at the Palmar Carpal Ligament and attaches to the Deep Digital Flexor Tendon.
Tendons Of The Lower Leg
Tendons are bands of fibrous tissue that join muscle to bone.
- Superficial Digital Flexor Tendon
This originates from the Superficial Flexor Muscle and attaches to the Long and Short Pastern Bones.
- Deep Digital Flexor Tendon
This originates from the Deep Digital Flexor Muscle and runs down the back of the lower limb going behind the Navicular Bone before attaching to the Pedal Bone.
- Common Digital Flexor Tendon
This originates from the Common Digital Flexor Muscle and runs down the front of the lower limb attaching itself to the Short Pastern and Pedal Bone.
- Lateral Digital Flexor Tendon
This originates from the Lateral digital Flexor Muscle and attaches itself to the Long Pastern Bone.
External Structures Of The Lower Limb
- Hoof wall
The hoof wall is made up of tough tubular horn which grows continuously downwards from the coronary band to produce a tough hard outer shell that is made up of the protein Keratin and is insensitive. It is through the insensitive hoof wall that the hoof is trimmed and where the farrier will drive the nails through to secure the shoe with no pain being caused to the horse. The front of the hoof wall is called the toe and to the side are the quarters, the hoof wall is one of the weight bearing structures of the horses lower limb.
- Coronary band
This runs around the top of the hoof wall joining the top of the hoof wall to the skin of the lower leg, it is from here that the tubular horn continuously grows downwards form to form the hoof wall.
This is a protective barrier and it also helps to control moisture balance of both the hoof wall and coronary band, it covers both the very upper part of the hoof wall and the coronary band.
This is one of the weight bearing surfaces of the lower limb and it also acts as a shock absorber. It is triangular in shape and is made of a flexible rubbery substance that upon contact with the surface flattens pushing outwards against the hoof wall and Bars and also up against the Digital cushion, when the lower limb is lifted from the ground the pressure against the Frog, Wall, Bars and Digital Cushion is relieved and it is through this pressure that the horses weight is distributed and that blood circulation in the lower limb occurs. Down the centre of the Frog there is a groove called the Sulcus and this groove extends to the bulb of heel.
This is situated underneath the hoof where it joins with the frog and walls of the hoof. A healthy sole will be free from cracks and punctures. The area of sole between the heel walls and the bars is called the seat of corn.
These are situated at the back of the hoof
This is another of the weight bearing surfaces of the lower limb, and forms from the Hoof Wall at the heel where it curves inwards.
Internal Structures Of The Lower Leg
- Navicular Bursa
This is a fluid filled cushion which allows the deep digital flexor tendon to smoothly run over the Navicular bone on route to the pedal bone.
- Digital Cushion
This is situated within the heels and is made of a flexible material that acts with the Frog to provide weight distribution
Sensitive Structures Of The Lower Limb
- Sensitive Laminae
Within the hoof there is tissue called sensitive laminae and it is this tissue that provides nutrients and blood to the internal structures. Directly below the sensitive Laminae is the Digital Cushion.
- Horny Laminae
This surrounds the Sensitive Laminae and is not sensitive its purpose is to join to the hoof wall via the White Line.
- White line
This runs around the rim of the hoof and sits between the hoof wall and the horny laminae.