Discussion of the Equine Knee

...and on the eighth day God created the horse in perfect image, to romp, graze, gallop, play and make manure wherever it darn well pleases, in divine grace.

When looking at a horse, we commonly refer to “Carpus” as the knee of the animal, but anatomically speaking, it actually ties in with the human wrist. (1)

The knee is a very complex structure made up of many small bones. The entire joint consists of three major joints, the Carpmeta-carpal joint, the Intercarpal joint and the Radiocarpal joint. (2) All work together for gliding and sliding and extension and flexion. Ligaments bind them all together.

Good conformation requires the knee to be of adequate size, balance and definition, in proportion to the rest of the horse. It should not look round, like a human knee, but flat, especially when viewed from the front. This aids in providing a smooth surface for the up and down action of the knee.

The knee should be wide when viewed from the side, and a nice line should be formed by the cannon and forearm, with no distortion. The leg should form a nice line from shoulder down to hoof.

Poor conformation at the knee will affect the weight-bearing capability of the entire leg, thus affecting the entire animal in its ability to work and haul. With poor conformation, impact of force, along with concussion, is not equally distributed over the bones in the leg. (3)

Thus, some parts of the leg and knee only receive partial stress of impact, while other parts receive more stress and impact. This will set the horse up for problems and injuries which involve the lower leg and knee, along with the fetlock joint, further down.

When buying a horse, always give a long look at the horse from the side, from a good distance out.

Faults may be viewed at this angle, such as “bucked” or “sprung” knees.

“Bucked knees” is a fault where the knee is distorted toward the front, or the front leg bends forward at the knee. “Calf knees” have the knees distorting backwards, or where the front leg bends backward at the knee.

“Tied in” at the knee has the flexor tendon too close to the cannon bone just below the knee. The cannon bone is too small here and the tendons will not be able to support the horse under stress.

This conformation fault can ruin free movement of the animal and the severity of the fault will show in direct proportion to movement lost. (4)

“Cut out” under the knees exhibits a dent or cut out appearance, in front of the cannon bone, just under the knee.

When the animal is viewed from the front, faults such as “knock knees” can be seen, with the knees stuck in toward each other. It is also called “in at the knees.”

“Bow legs” can look like old cowboy legs, where the knees are stuck out in a noticeable arc away from each other. (5)

“Bench knees” or “offset knees” show the cannon bone being offset outside the knee; the leg does not follow a straight line. Horses with this conformation defect a very prone to breaking down when under hard work.

Knees of young horses are x-rayed to determine age, and whether the knees have “closed.”

The method attempts to determine maturity of the animal, and whether it will be able to withstand hard work. As the body grows, the bones increase in size and length. When x-rays are interpreted by a qualified person, such as a Veterinarian, the “growth plate” or epiphysis of a bone will show whether the bone is still growing. (5)

The lower or distal epiphysis of the long bone in the forearm, or the radius, is the most common site used by Vets to make age and maturity determination.

As the epiphyseal cartilage continues growing, so the bone continues to grow in length. Cartilage gradually changes into bone at this site, over a period of time. When the cartilage stops growing it changes into bone, and all growth ceases.

When you hear the trainer talking about a young colt being “closed at the knees,” it means the colt has reached a maturity level suitable for certain types of work or more lengthy training sessions.

The openness appears as a horizontal epiphyseal line on the x-ray. These lines disappear when the knee is considered “closed.”

Always consult a qualified Vet for taking and viewing radiographs, along with the usual “Vet check” of the animal when purchasing or looking to buy.

More next time. Stay warm.

Closing with the immortal words of Roy Rogers and Dale Evans, “Happy Trails to You.”

1-5: “Horseman’s Veterinary Encyclopedia,” by Will A Hadden III, DVM