ACL Injuries are RUFF!
ACL Injuries are NOT Just a Skiers Problem in the Mountains!
What is an ACL or Anterior Cruciate Ligament?
Anterior Cruciate Ligament or ACL, other wise known as the Cranial Cruciate Ligament or CCL when referring to pets is a vital support structure of the knee. This ligament’s primary role is to provide and maintain stability to the knee. The knee’s anatomy in the most simple of descriptions contains two cruciate ligaments that cross inside the knee joint and provide stability of the upper femur and lower tibia while cartilage cushions called medial and lateral menisci rest between the tibia and femur to create a soft barrier between the two bones. A support bone called the Fabellae flanks the tibia on the side while the knee cap or patella slides up and down the front of the knee during flexion and extension. The anterior cruciate ligament prevents the tibia from sliding forward out from under the femur.
How does a dog injury their ACL or CCL?
The most common cause of cruciate ligament rupture is excessive internal rotation of the tibia when the joint is partially flexed. This can be the result of trauma or running and planting the hind limbs while the momentum of the body continues to move forward.
What factors can increase the chance of an ACL or CCL injury?
Conformational deformities of the knee such as patella laxation contribute to repeated stress on the CCL, obesity increases the stress on support structures, animals over 5 years of age demonstrate a decrease in strength and stiffness of these structures, animals that have ruptured one CCL are more inclined to rupture the opposite side in 1 to 3 years, and finally immune mediated diseases may weaken and eventually lead to complete failure of one or both CCLs. Recent studies have also identified specific breeds that appear to be more predisposed to ACL or CCL injuries such as: Mastiffs, Newfoundlands, Akitas, St. Bernard's, Rottweilers, Chesapeake Bay retrievers, American Staffordshire terrier, and Labrador retrievers.
What are the signs of a ruptured cruciate ligament and how is a diagnosis made?
A ruptured ACL or CCL is the most common knee injury of dogs; in fact in most cases a sudden lameness of the hind limb tends to be a ruptured cruciate until proven otherwise.
The most common signs include: sudden pain of the hind limb, swelling of the knee, instability of the knee, or hindlimb weakness.
The key to diagnosis of a ruptured cruciate ligament is the presence of a type of knee instability called a cranial drawer sign. This is where the tibia moves forward on palpation from the femur like the motion of a drawer being opened. Often in large painful dogs this test is best performed when the dog is sedated to allow for the knee to be completely relax. Other important supportive diagnostics used may include: radiographs, MRI, and arthroscopic surgery.
How to treat a ruptured ACL or CCL and when to act?
Rupture of the cruciate ligament results in progressive and degenerative changes with in and around the joint, therefore surgery is the most proven and consistent way to treat a ruptured ACL. Historical data also demonstrates that dogs that start with a partial ACL tear almost always result in a full ACL tear in a matter of weeks or a few months. Early surgical repair has demonstrated a more complete and quicker recovery with less chances of progressive cartilage damage or weakening of the opposite leg’s cruciate ligament. Surgeries that are commonly performed can be divided into intra-articular versus extra-articular and arthroscopy versus arthrotomy. Most common surgical techniques include: Extracapsular repair (used almost exclusively in small dogs), Tibial Plateau Leveling Osteotomy (TPLO), and Tibial Tuberosity Advancement (TTA) are most commonly used in medium to large breed dogs. Typically dogs who have undergone surgery are supporting weight by 10 days and full function is achieved in 3 to 4 months.
Early detection and treatment of a ruptured ACL or CCL will heal quicker and better with less chance of debilitating arthritis in the future or tearing of the adjacent ACL. Factors to identify early that may predispose your pet to an ACL injury are: conformational deformities, obesity, animals over 5 year of age, immune mediated diseases, specific breeds, and a history of a previous ACL tear.
Author: Dr. Charlie Meynier
Feel free to email questions to firstname.lastname@example.org. Veterinarians Charlie Meynier and Tom Suplizio practice at the Vail Valley Animal Hospital and ER, with locations in Eagle-Vail and Edwards that offer comprehensive small animal medicine and surgery.
On-call vets are available after hours, and an emergency hospital in Edwards is open 24 hours a day, with a doctor on the premises weekends and holidays. For more information, call 970-926-3496 or visit www.vailvalleyanimalhospital.com.