Anatomy of the Canine Front Limb

Original Editor - Ansi van der Walt Top Contributors - Jess Bell, Chelsea Mclene, Tarina van der Stockt, Robin Tacchetti, Kim Jackson, Vidya Acharya, Lucinda hampton and Olajumoke Ogunleye

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This page introduces the anatomy of the canine front limb, also known as forelimb and thoracic limb.

Skeletal System

The bones of the front limb are:

• Scapula
• Humerus
• Radius
• Ulnar
• Carpus
• Metacarpals
• Phalanges

Specific Features of the Canine Skeleton

• While dogs do have a clavicle, it is a rudimentary structure within the brachiocephalicus muscle and it is rarely seen on x-ray
• There is a narrow band of scapula cartilage along the dorsal border
• Both dogs and cats have a supratrochlear foramen on their humerus. Nothing passes through this gap in dogs. In cats, the median nerve and brachial vessels pass through this foramen
• There are no significant modifications of the radius and ulnar bones
• There are seven carpal bones - this is due to the fusion of the radial and intermediate carpal bones, thus forming the canine “radial” carpal bone
• The first metacarpal is significantly reduced - it has only two phalanges (P1 and P3) and is a non-weight bearing structure. It only has one associated sesamoid bone and is known as the “dew claw”
• The distal phalanx carries the horny claw. The flexor process (palmar) is where the deep digital flexor tendon inserts. The extensor process (dorsal) is where the common digital extensor tendon inserts
• The ungual process is a cone shaped process covered by the horny claw
• Sesamoids
  • Proximal - pared articulating with MII dorsal. The axial surface is joined by a thick inter-sesamoidean ligament
  • Distal / navicular - boat-shaped, articulated with P2 and P3. Provides a bearing surface for the deep digital flexor tendon, which places it under significant compressive stress

The following videos describe the skeletal system of the canine front limb in detail. The second video discusses other animals as well. The front limb is discussed from 49:11 minutes to 59.37 minutes.

Joints of the Canine Front Limb

Scapulo-trunk (scapulo-thoracic)

• Type
  • Synsarcotic joint with no attachments (i.e. no clavicle)
• Supporting structures
  • A series of muscles that sling the trunk from the scapula. This allows for shock absorption and increases range of motion
• Joint motion and range
  • Cranial glide (NB: caudal, dorsal and ventral glide are described, but not quantified)
  • Winging, tipping and rotation are not described

Shoulder (glenohumeral)

• Type
  • Ball and socket joint
  • Consists of glenoid cavity of the scapula and the head of the humerus
  • The glenoid fossa on the scapula is deepened by the glenoid labrum
• NB: shoulder flexion (and extension) is not the same as limb flexion (and extension). Limb flexion (i.e. protraction) involves shoulder extension
• The biceps tendon lies over the cranial aspect of the joint and it is held against the humerus by the transverse humeral ligament
• Glenohumeral ligaments are thickenings of the joint capsule, not true ligaments
• There are no other ligaments
• The synovial sheath of the biceps brachii tendon is an extension of the joint capsule