Patellar Ligament Injuries in Horses

Injuries to the patellar ligaments are typically rare in horses, though they are more likely in animals with jobs that put stress on the knee joint, also known as the stifle. Horses who spend a significant portion of their daily lives running or jumping tend to put more stress on the ligaments than horses with less athletic lives. Damage to the tendons and ligaments in this area take a great deal of time to heal and may require a limited amount of motion and exercise during that time.

Horses with injuries to the ligaments of the stifle joint usually require a lengthy recovery period with restricted exercise in order to heal completely.

Most of the signs that indicate that a horse is lame, whether from ligament injuries, hairline fractures, or degenerative bone disorders, are apparent even to the untrained eye; although some may be more subtle and difficult to spot: 

• Behavioral changes
• Generalized limping
• Heat and swelling near joint
• Inability to put weight on the limb
• Poor performance
• Reluctance to stand 

Types 

The patellar ligaments that are found in the knee joint are not the only ligaments that contribute to the strength of the knee. Other important ligaments include:

• Collateral ligaments - Located on the inside and outside of the stifle joint these short, thick ligaments attach the femur to the tibia
• Medial and lateral patellar ligaments - These ligaments attach the patella to the tibia
• The anterior (forward) and posterior (hind) cruciate ligaments - These two strong bands cross each other within the joint and stretch between attachment sites on the tibia and the femur; these cruciate ligaments provide additional rotational stability as well as support for the joint when it is pushed too far forward or backward

Injuries to the ligaments located in the knee are usually caused by trauma to the joint itself. The stifle joint is a complicated joint involving several bones, tendons, and ligaments. The kind of injuries that lead to the ligaments in the knee being torn or stretched are much more common in jumping horses and animals who regularly make sharp turns at high speed than in pleasure horses or horses who have more laid-back lives.

When a hind limb is involved in an injury, it may be most apparent when viewing the horse from behind. The foot placement may appear odd, and the stride may be shorter on one side than the other, but the dragging of the hoof is likely with hind limb injuries. When the horse walks, it may lift its hip on the lame side to avoid putting as much weight on it and will allow the other side to dip a little bit to compensate, or with a knee injury it may swing the leg out wide in order to avoid bending the joint when walking.

These signs will prompt your veterinarian to use additional imaging technology. A radiograph, or x-ray, will probably be attempted first. Although useful in diagnosing damage to the bones themselves, injuries to the soft tissue like the ligaments and tendons will not show up on x-rays. The image may show evidence of damage to the ligaments, however, such as a patella that is out of place. A definitive diagnosis of this disorder will be made using imaging technology that is designed for viewing softer tissues, such as MRI imaging or an arthroscopy.

The treatment for a patellar ligament injury will depend on the amount of damage done to the ligament. Any damage to ligaments or tendons in the legs will require exercise restriction, rest, and hand walking. These measures are needed in order to reduce the load on the damaged leg so that healing can take place. Pain management medications, usually in the form of NSAIDs, are also frequently employed to reduce the inflammation and vasodilation, although it is essential only to use NSAID drugs as directed as they can quickly become toxic at higher doses. Several types of newer treatments have been made available to correct stretched or torn ligaments, and these can include:

• Bone marrow aspirate concentrate - A concentrated form of your horse’s own bone marrow, including both growth factors and stem cells, is injected into the joint or ligament
• Platelet-rich plasma - The veterinarian collects and concentrates plasma from the patient’s blood, then injects it into the joint or ligament
• Stem cell therapy - Stem cells harvested from either bone marrow or fat are injected into the joint or ligament

After equine surgery, you will be given specific instructions from your veterinarian regarding post surgery care. Restricted exercise will be required for full healing, particularly with bone, tendon, or joint surgery. Injuries to the stifle joint involve a lengthy stall confinement, sometimes up to six months, to facilitate healing and regrowth particularly when the tendons or ligaments are involved. This kind of confinement can be difficult for many horses, and depending on the temperament of the horse, sedation treatments may be required to keep the patient calm during this healing period. Once they are allowed out of their stall for exercise, they will most likely need hand-walking and close supervision until the joint is suitably restored.