Front Limb Conformation

What are the bones of the forelimb

• Scapula

• Humerus

• Radius

• Ulna

• Carpus

• Metacarpus

• Digits

• Sesamoids

Scapula

• Aka the shoulder blade

• prominent spine

• glenoid cavity

What does the glenoid cavity of the scapula articulates with

the head of the humerus

The humerus

• articulates with shoulder and elbow

what joint is the only joint in the forelimb that can abduct and adduct and is important for lateral movements

the shoulder joint

how can the length of the humerus be determined

by looking at the point of the shoulder to the point of the elbow

What does the length and angle of the humerus play a significant role in

the motion of the front limb

what does a long humerus provide

• more leverage for a longer stride

• increased mobility of the elbow → both extension and flexion

what is the desirable length of the humerus and what is the desirable angle

50-60% of the length of the scapula; 90 degrees between the humerus and scapula

how does the length of the humerus provide proper positioning of the elbow

by allowing the elbow to lie under the withers

too long humerus:

horses front legs are positioned too far under the body → can cause pigeon breast

too short humerus

horses front legs are positioned too far in front of the body

how should the elbow be positioned in relative to the forearm

in a line

from the rear view the elbow:

the olecranon should be vertical

from the side view the elbow

the point of the elbow should be positioned in a line with the front of the withers

what is Tied-In elbow

point of the elbow is too close to the body

what does Tied In elbows cause

• toes to point laterally

• horse to “wing in” when traveling and can also place feet directly in front of each other

• associated with a narrow chest

What is Turned-Out elbow

point of the elbow is too far from the body

what does Turned-Out elbows result in

• paddling motion when traveling

• possibly pigeon-toed and a base narrow

Radius and Ulna make up the and articulates with

• forearm

• humerus → elbow

• carpal bones

what two features does the ulna have

• olecranon

• the ulna is fused

the forearm

• should be strong and well developed

• should align with the carpus and cannon bone when viewed from all angles

the distal limb is made of

• carpus

• metacarpus

• digits

• sesamoids

the carpus

• 7 short bones → two rows of 6

• accessory carpal bone

Metacarpus

• horses stand on the 3rd called the cannon bone

• 2nd and 4th are splint bones

digits are composed of

3 phalanges

where are the two sesamoid bones

behind the fetlock and the coffin joints

the carpus makes up what joint on the horse

the knee

how many joints are in the carpus (knee)

3

what are the 3 joints that carpus contains

• Radiocarpal

• intercarpal

• carpometacarpal

what carpus joints are have high motion and what joints have low motion

High motion: radiocarpal and intercarpal

Low motion: carpometacarpal

describe the confirmation of the knee

• be directly in a line with the forearm and cannon bone

• large and flat on the front

• face directly cranial

• dorsal surface is smooth for extensor tendon located over the knee

• palmar surface is large enough for passage of flexor tendons

what can a misalignment of the knee cause

increases strain on various parts of the lower limb → specifically the fetlock joint

what is Calf Knee

the knee appears to be angled backwards due to the cannon bone being positioned too far palmarly under the carpus

why is Calf Knee bad

• puts extreme stress on soft tissues

• excessove forces applied during hyperextension that can lead to fractures in the carpal bones

what are Bucked Knees

“over at the knees” and the knees are slightly bent. Can be caused from genetics or over-use

why is Bucked Knees bad

can increase strain on the dorsal fetlock joint and palmar carpal joint

what is bowlegged

knees deviate laterally when viewed from the front

what can bowlegged be accompanied by

pigeon-toe and base-narrow conformations

What is Knock-Knees

the knees deviate medially when viewed from the front

Knocked-knees mild deviations vs severe

mild: may not be a problem

severe: puts excess strain on limbs

what is the common name for metacarpal III

cannon bone

the cannon bone

• should be vertical

• should align under the carpus

• should be smooth

• flexor tendons should be set off the cannon bone

how does the length of the front cannon bone relate to the length of the back cannon bone

a short front cannon bone and a longer rear cannon bone is ideal because it increases the structural support of the limb

what are benched knees

the cannon bones are not in alignment with the forearm when viewed from the front of the horse

what does bench knees result in

excessive forces on the medial side of the cannon bone and the entire lateral surface of the distal limb

• commonly results in medial “splints”