A dog tearing its ACL is a painful and unpleasant experience for the dog and its owner. Our Bellevue vets explain the causes and treatments of this condition, including the often necessary cruciate surgery associated with it.
What Are the ACL & CCL?
In the human knee, there is a thin piece of connective tissue called the anterior cruciate ligament (ACL) which connects the lower leg bone (tibia) to the upper leg bone (femur) and helps the knee to function. Dogs also have this connective tissue joining their tibia and femur however, in dogs it's called the cranial cruciate ligament (CCL).
While the human ACL and the dog's CCL function somewhat differently, pet owners and vets will often refer to the dog's cranial cruciate ligament as the dog's ACL, CCL, or 'cruciate' interchangeably.
How Do ACL Injuries Occur?
Dog ACL injuries typically come on gradually rather than suddenly and tend to become progressively worse with activity. There may not have been a defining moment when your dog suddenly injured their ACL, but through continued exercise symptoms that began as mild will gradually become more pronounced and painful for your dog.
An ACL injury can also occur if your dog takes a nasty fall, or even if they land awkwardly while running or jumping. If you do notice a single event occur resulting in a possible ACL tear, seek emergency veterinary care immediately.
What Are the Signs of an ACL Injury?
Dogs with an ACL injury cannot walk normally and experience pain. If your dog has injured their ACL you will likely notice that they are limping in their hind legs, experiencing stiffness following exercise, and will likely have difficulties rising off of the floor or jumping.
How Are ACL Injuries in Dogs Treated?
If you suspect that your dog has an injured ACL it is important to have your vet diagnose and treat the condition.
If your dog's ACL is torn or injured, the tibia (lower leg bone) slides forward in relation to the femur (thigh bone). This movement is known as a 'positive drawer sign' and results in knee instability which could cause damage to the cartilage and surrounding bones, or possibly lead to osteoarthritis.
Surgical treatments for ACL injuries in dogs include:
Extracapsular Lateral Suture Stabilization - ELSS / ECLS
This surgical treatment for a torn ACL in dogs works by counteracting 'tibial thrust' (the sliding forward of the dog's tibia) with a specifically placed suture.
Tibial thrust is caused by the transmission of weight up the tibia and across the knee, causing the tibia to “thrust” forward relative to the femur. The forward thrust movement occurs because the top of the tibia is sloped, and the dog's injured ACL which is normally able to oppose the forward force, is no longer able to prevent this unwanted movement.
Extracapsular Lateral Suture Stabilization corrects tibia thrust by “anchoring” the tibia to the femur with a surgically placed suture. The suture pulls the joint tight and helps to stabilize the knee, preventing the front-to-back sliding of the femur and tibia while the ACL heals and the muscles surrounding the knee strengthen.
The suture must stay intact for 8-12 weeks for the ACL injury to heal. The suture will then begin to loosen or even break.
This surgery is relatively quick and uncomplicated with a good success rate in smaller dogs. It can also be less expensive than other methods for repairing a torn ACL in dogs. Long-term success varies in dogs of different sizes and activity levels.
Tibial Plateau Leveling Osteotomy - TPLO
Another surgical option for treating your dog's injured ACL is the tibial plateau leveling osteotomy (TPLO). This surgery is more complex than the ELSS and aims to reduce the amount of forwarding movement during the dog's stride without the help of the ACL (CCL).
In this procedure, a complete cut is made through the top of the tibia (tibial plateau). The tibial plateau is then rotated to change its angle and a metal plate is added to stabilize the cut bone as it heals. The tibia will gradually heal and strengthen over several months.
Full recovery from TPLO surgery will take several months however some improvement can be seen within just days of surgery. It is essential to follow your vet's instructions after your dog's TPLO surgery, and restrict your dog's activities to allow the bone to heal properly.
The long-term prognosis is good for TPLO treatment in dogs, and re-injury is uncommon. The stabilization plate does not need to be removed from your dog's leg unless it begins to cause problems.
Tibial Tuberosity Advancement - TTA
Tibial Tuberosity Advancement surgery is similar to TPLO but may be slightly less invasive than TPLO. Recovery from TTA appears to be quicker than recovery from TPLO in many dogs.
When TTA surgery is performed the front part of the tibia is cut and separated from the rest of the bone. Next, a special orthopedic spacer is screwed into the space between the two sections of the tibia to move the front section forward and up. By doing this, the patellar ligament which runs along the front of the knee is moved into better alignment and helps to prevent much of the abnormal sliding movement. Once this process has been completed, a bone plate will be attached to hold the front section of the tibia in its proper position.
TTA surgery is typically performed in dogs with a steep tibial plateau (angle of the top section of the tibia). Your vet will evaluate your dog's knee geometry to determine which ACL treatment surgery is best for your dog.
What Is the ACL Surgery Recovery Process?
All dogs are different and some dogs will recover more quickly than others following ACL surgery. Nevertheless, recovery from ACL surgery is always a long process!
Your dog may be able to walk as soon as 24 hours following surgery, however full recovery and a return to normal activities will take 12 - 16 weeks or maybe longer.
It is essential to follow your vet's instructions and to pay attention to your dog's healing progress. Never force your dog to do exercises if they resist as this can lead to re-injuring the leg.