Os metacarpale/metatarsale III
The single large bone below the knee (MC3) or hock (MT3). Horses evolved to run on a single digit, and the cannon bone is the main shaft of that digit. The splint bones (MC2/MC4 and MT2/MT4) are vestigial remnants of the second and fourth digits. The cannon bone is subcutaneous (just under the skin with no muscle covering) making it vulnerable to direct trauma.
Origin: N/A (bone)
Insertion: N/A (bone)
Action: Bears the entire body weight on a single digit; key structural adaptation for speed
The cannon bone is subcutaneous and easily palpated. Condylar fractures are the most common catastrophic injury in racehorses. Dorsal metacarpal disease (bucked shins) is common in young horses entering training.
Fractures through the distal condyle of the cannon bone, often propagating from stress fractures during racing. The most common catastrophic fracture in racehorses.
Stress remodeling of the dorsal cortex of the cannon bone in young racehorses entering training. The bone is adapting to the new loading demands.
Fractures or bony growths (splints) on the second or fourth metacarpal bones. Splints are common in young horses beginning work and are caused by tearing of the interosseous ligament between the splin
The cannon bone (MC3/MT3) is the main weight-bearing bone below the knee or hock. Splints, stress fractures, and bucked shins are common injuries here, especially in young racehorses. The splint bones run alongside and can fracture or develop bony calluses. View in 3D at /explore. Related: /blog/horse-leg-anatomy-guide
Fractures through the distal condyle of the cannon bone, often propagating from stress fractures during racing. The most common catastrophic fracture in racehorses. Signs include: Acute severe lameness or breakdown during racing; non-weight-bearing; sometimes visible angulation of the fetlock; often an open fracture; the number one cause of racehorse fatalities on track.; Consult veterinarian for specific symptoms.
Stress remodeling of the dorsal cortex of the cannon bone in young racehorses entering training. The bone is adapting to the new loading demands. Signs include: Pain and swelling over the front of the cannon bone; worse after fast work; warm to touch; common in 2-year-old Thoroughbreds in early training; usually self-limiting with rest and controlled exercise.
Fractures or bony growths (splints) on the second or fourth metacarpal bones. Splints are common in young horses beginning work and are caused by tearing of the interosseous ligament between the splint and cannon bones. Signs include: Warm, painful swelling on the inside or outside of the cannon bone; lameness in acute phase; bony hard lump after healing (cosmetic blemish); usually resolves with rest; rarely causes long-term lameness unless near the knee or suspensory.; Consult veterinarian for specific symptoms.; Hard, warm, painful swelling on the side of the cannon bone; lameness (may be temporary); cosmetic blemish after healing; splint fractures can irritate the suspensory ligament if displaced.
The cannon bone is subcutaneous and easily palpated. Condylar fractures are the most common catastrophic injury in racehorses. Dorsal metacarpal disease (bucked shins) is common in young horses entering training.
The cannon bone (MC3/MT3) is the main weight-bearing bone below the knee or hock. Splints, stress fractures, and bucked shins are common injuries here, especially in young racehorses. The splint bones run alongside and can fracture or develop bony calluses. View in 3D at /explore. Related: /blog/horse-leg-anatomy-guide
See the Cannon Bone (Third Metacarpal/Metatarsal) on our interactive 3D horse model. Open 3D Model