Stifle Lock: Identification and Alternative Therapies

While not always the cause of lameness, a performance horse's stifle is often suspect when he comes up lame. Several different types of stifle lamess exist, but the purpose of this article is to discuss upward patellar fixation (UPF), otherwise known as stifle lock.

Horses naturally stand in a way that allow their muscles to exist in a resting state, and remain upright without muscular contraction. This allows a horse to remain standing upright while asleep without muscle fatigue.

Stifle lock involves alignment issues with the knee. In a healthy horse, flexing of the stifle causes the patella to glide down the trochlear grove, which is held in place by several ligaments. In performance horses, owners often see what is described as a loose stifle. In this instance, the patella intermittently does not travel along its designated path, which may lead to one or more of the following symptoms:

• Difficulty cantering downhill

• Difficulty collecting

• A noticeable stumble in the horses' step

• The horse dragging/not picking up one or both of his legs

• When moving, the horse does not step underneath itself and has difficulty tracking. This may be visible in one or more gaits

• The horse stands in a “parked out” position

• In its most debilitating form, the leg extends outward with the fetlock resting on the ground

  
  

  Note: While not always the case veterinarians commonly see UPF in horses with very straight hind legs. These horses are sometimes referred to as “post legged”.

  
  

Generally, the first line of defense recommended by veterinarians will be to work on collection exercises. For many performance horses, collection work is a “given” and it remains a problem. These horses are may also have difficulty transitioning and if they don't get upset about the stifle pain, simply appear to chronically resist or not understand collection. For horses that are in poor physical condition, a strict physical regimen may be all that is needed. The toning and tightening of the muscles return the stifle to its original form. Water treadmill work is sometimes recommended as it puts less stress on the joints.

Let's go back to the case of performance animals, who are assumedly in top physical condition. These animals have excellent top-lines and a high level of fitness. For such animals. I personally utilize an animal practitioner that is both a chiropractor and licensed veterinarian for all major orthopedic ailments. I have found that a good chiropractors have excellent eyes for diagnosis and often have much less invasive means of treatment.

One practice that is relatively common, but controversial in the equine world is called “blistering”. Blistering occurs when a veterinarian injects a chemical irritant, such as iodine and almond oil, into the stifle. The irritant causes inflammation, scar tissue and subsequent ligament thickening and soft tissue contraction, all which help hold the patella in place. This is combined with a low intensity physical regimen that is used to build up strength around the joint.

Other treatments include steroids and surgical techniques. Surgical techniques may be more mainstream, but they are a lot more extreme. Once a tendon is cut, it will never be the same. As with any animal health decision, be sure to consult your veterinarian.

In our personal experience, we had our mustang, Zero, blistered this spring. We had trouble with his stifles catching, which would cause him to buck, especially downhill at the canter. Combined with 20 minutes of daily collected trotting, he has become a completely different horse.

Now that his stifles no longer catch, his bucking has completely stopped. His rear end has changed shape, and the tensor muscles that we previously had difficulty building up became strong in a matter of weeks. It is important that we keep him in good shape, or we were warned that stifle lock could return.

One thing I have learned from this experience is if you are an experienced rider and continue to see a persistent “behavior” problem, it is important to consult a physician rather then to battle your horse. Zero is now so trustworthy that I can walk, trot, canter and jump with him bareback.