Lameness in the horse’s stifle joint can result in shortened stride length, reluctance to work or a rough canter. While lameness is more commonly attributed to problems with the hock joint, stifle lameness is seen frequently in performance horses.

The stifle is a complex joint in the horse’s body with a similar function to the human knee. Stifle injuries can result from repetitive stress, trauma, excessive use, changes in direction and rapid deceleration. Horses engaged in jumping and barrel racing are most at risk of these injuries.

Stifle lameness does not always mean the end of a horse’s athletic career, although it may mean the animal will never again perform at its previous level. The good news is that diagnosis and treatment of stifle lameness have improved significantly in recent years. [1]

Advancements in imaging technology have made a significant difference in the ability of veterinarians to make accurate diagnoses of what formerly may have been deemed an “unknown” lameness.

Prevention of stifle lameness and other stifle injuries starts with ensuring your horse is not overworked and supporting overall joint health. It is important to keep excess weight off of your horse and to be vigilant for any signs of over-use.

The Horse’s Stifle Joint

The stifle is one of the most complicated parts of the equine body. The stifle is designed for flexion and extension of the hind leg.

The stifle is the largest joint in the horse’s body and the site where the femur meets the tibia in the hind end.  The former is the long bone between the hip joint and the stifle, while the latter is the bone running between the stifle and hock.

Also involved in the stifle joint is the patella, or kneecap, situated on the femur’s lower end. This small, flat, round bone is attached to the thigh’s quadriceps muscle.

The patella sits in the trochlear groove on the femur. From this groove, it slides up and down as the rear leg moves.  The patella’s movement lets the joint move like a hinge. The leg is able to extend and flex, but it cannot move sideways.

Stifle Joint in Horses | Mad Barn Canada

Anatomy

Three shock-absorbing joints are involved with these bones:

  • Medial femorotibial joint
  • Lateral femorotibial joint
  • Femoropatellar joint

On the outside edges of the joint, the short, thick, medial and lateral collateral ligaments join the femur and tibia bones. Deep within the cleft area are the anterior and posterior cruciate ligaments (ACL and PCL).  These ligaments aid in joint stabilization.

In total, 14 ligaments hold the joints together. There are also the two menisci, discs cushioning the femur and tibia.

Stifle vs. Human Knee

The stifle is the equivalent of the human knee. However, when people stand still, their knees are upright. The equine “knee” is angled.

Although anterior or cranial cruciate ligament ruptures are common injuries in human and dog knees, this injury seldom occurs in horses.

In people, just one patellar ligament comes off the kneecap. Equines have three such ligaments.  If a horse does suffer a severe cruciate ligament rupture, options for the animal are limited.

Types of Stifle Disorders

With such a complex joint, it is unsurprising that there is a considerable range to stifle lameness. [2]

For instance, intermittent upward fixation of the patella frequently afflicts young horses. The condition is sometimes referred to as “sticky stifles” or “catchy stifles”. In some pony breeds, this is an inherited condition.

The stifle has a locking mechanism that allows the horse to stand while sleeping. That is a normal process. A sticky stifle means that this mechanism is keeping the leg in a locked position.

In many cases, regular exercise can strengthen muscle and ligament tone sufficiently to prevent the hitched gait inherent in upward fixation of the patella.

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Signs and Symptoms of Stifle Lameness

Initially, signs of stifle lameness are often subtle. Horses may seem off when taken out of their stalls, but get better as they continue working. A long period of stall rest and subsequent loss of muscle and ligament tone may exacerbate the problem.

Reluctance to work may prove an early indicator of a stifle issue. Other signs of weak stifles in horses include:

  • D