Stifle Injuries in Horses

The most complex joint in the horse is the stifle joint. The joint includes the kneecap and its ligaments, which give structural stability. Similar to the human knee, the stifle is located on the horse’s hind limbs. Encircling the whole stifle joint is a thin capsule that has a special fluid that assists with shock absorption and lubrication. Certain ligaments that cause the leg to not bend too much in either direction are present inside and outside of the stifle. 

When properly working, the stifle allows the horse to be stable as well as smoothly move forward. Should he experience trauma, quick directional changes or deceleration, it will cause pressure that can lead to stifle injury. Due to the somewhat open construction of the stifle, as well as its size, swelling will often develop. Serious stifle injuries are often made more complicated due to fractures.

Trauma to the stifle, the horse’s most complex joint, can lead to stifle injury; in addition, some horses experience developmental disorders of the stifle, which will impact them as foals or young horses.

Should your horse experience a stifle injury, you may witness the following:

• Swelling
• Lameness
• Seemingly intolerant of exercise
• Kneecap locking up
• Joint thickening

Types 

Trauma along with different diseases can impact the stifle. Often, stifle diseases are divided into two types:

Acquired Disorders

This includes arthritis, degenerative joint disease, fractures and trauma (like an injury to the cruciate ligament). These issues result from infection, bacteria or trauma. Sudden and severe onset with sudden and obvious lameness and swelling point to an acquired disease in the stifle.

Developmental Disorders

These diseases are present at the time of birth and may or may not be the result of genetic abnormalities. Developmental disorders of the stifle typically impact foals and young horses who will initially show subtle symptoms. As the horse gets older and begins training, you will see swelling of the stifle and ongoing, low level lameness. Often the lameness and swelling will be very obvious with continuous exercise, and then decrease when activity is reduced. Examples of developmental disorders include osteochondritis dissecans, subchondral bone cysts and patellar luxation.

After conducting a physical examination of your horse, your veterinarian will use a variety of methods, to include digital x-rays, ultrasound and curvilinear ultrasound probes in examining the stifle joint and making a diagnosis. These tools will help your veterinarian get images of the different parts of the joint. Exploratory arthroscopic surgery may be useful when trying to determine the cause of the problem. Intra-articular anesthesia of the stifle is often key in diagnosing the problem and is used to localize the lameness. 

It is important for your veterinarian to get an understanding of which part of the stifle is impacted and what is causing the problem in order for him to recommend the correct treatment.

Once your veterinarian has diagnosed the stifle injury in your horse, treatment will vary based upon the specific injury or disease. Rest will be recommended in order to alleviate the swelling and provide the opportunity for the joint to begin to heal. In cases where the joint capsule is stretched and not ruptured, recovery can happen with 2-3 months of rest and a slow return to activity. When inflammation is present, intra-articular medication may be recommended.

If there is a lesion present on radiography or if there has been no resolution to symptoms after a period of rest possibly including intra-articular medication, surgery may be considered. When the collateral ligament or cruciate ligaments are injured, treatment will frequently not be effective. This will lead the joint to become unstable and can progress to arthritis and ongoing lameness.

Should your horse be diagnosed with a stifle injury or condition, you will want to follow the recommendations of your veterinarian to ensure the best outcome for him. It is likely that follow up appointments will be recommended so that your veterinarian can assess the condition of your horse’s stifle and determine whether treatment is effective.

There are things that you can do to prevent stifle injuries in your horse. You can help him avoid direct trauma to the joint by not pushing him past his abilities, particularly in performance activities. It is important to keep an eye on your horse and be cognizant of any possible stifle injuries and act right away if you notice anything of concern by having your horse examined. The stifle joint is complicated and hard to evaluate with radiography because of its mass, surrounding tissue and soft tissue structures.