ACL stands for “anterior cruciate ligament,” although in dogs and cats it’s more commonly referred to as the CCL, or “cranial cruciate ligament.”
The CCL is a small ligament located inside the knee joint, and it plays an important part in keeping the joint stable, in an appropriate position, and functioning well.
ACL tears are fairly common in dogs — especially medium- to large-breed dogs. The condition is uncommon in cats, although it can happen.
What are the causes of a tear?
Compared to human beings — who stand with their knees in a straight line — dogs have a slope inside their knees, which means their ACL has more of a weight-bearing function than human ACLs do.
So, in dogs, the ligament can just wear down from normal activities over time, even if no obvious injury occurs.
Unfortunately, that also means dogs who tear the ACL of one hindlimb are at risk of tearing the ACL in their other hindlimb at some point in their life.
Injuries, or other conditions that destabilize the knee joint (such as a luxating patella), can also lead to an ACL tear.
Also, overweight or obese pets have a higher risk, due to the increased weight that the knee joint needs to support.
What is an ACL tear and why is it bad?
An ACL tear means that the ligament is either partially torn or fully torn.
The ACL keeps the femur (thigh bone) and tibia (shin bone) in the right position relative to one another. If the ligament is torn, that means the tibia can slide further forward than it normally would — an effect that’s even more pronounced because of the shape of a dog’s knee, which slopes at more of an angle than human knees do. This results in painful inflammation and swelling.
In addition to pain from the injury itself, over time, this joint instability can lead to irreversible bone and cartilage damage and arthritis in the knee.
What are the signs of an ACL tear?
The first thing you’ll probably notice is your pet limping or holding the injured leg up and refusing to put any weight on it. Some pets may yelp, cry, or whine, but many pets won’t (dogs and cats are good at hiding pain, and may try to proceed with their daily activities despite being in pain).
If you look closely, you may also notice some swelling at the knee joint compared to the other leg — but this may be subtle and difficult to detect. The knee may also feel warm to the touch, and your pet might not want you to touch the affected leg.
Your pet may also hold the leg out to the side while sitting, and may be slower to rise from a lying down position.
Can you prevent an ACL tear?
Since genetics and natural dog physiology play a role in ACL injuries and tears, it may not be possible to prevent entirely. But, certain preventive measures may help with joint health, such as:
- A good quality joint supplement, like glucosamine and chondroitin. You can start supplements when your pet is young, and it’s an especially good idea if they’re in an at-risk category (medium- to large-breed dogs).
- Maintaining a healthy weight to reduce the pressure on your pet’s joints.
- An active lifestyle with moderate physical activity, which keeps your pet’s muscles and joints strong. If it’s been a while since your pet exercised, start slow and work your way up. And, try to do consistent activity rather than falling into the “weekend warrior” syndrome, where your pet is sedentary all week, then very active on the weekends.
Every pet is an individual, so ask your vet for a personalized recommendation for your furry family member.
How is an ACL tear diagnosed?
In order for your dog or cat to receive appropriate treatment, they need to be accurately diagnosed. Your vet will examine your pet to rule out other conditions that could cause your pet to limp (for example, a bone fracture).
Diagnosis for ACL tears includes:
- A full physical exam by your vet to determine the exact location of the pain, look for swelling or other symptoms, and check that your pet is otherwise in good health (in case surgery is needed).
- Feeling for “cranial drawer.” This is a specific type of palpation and movement of the knee joint that tests for instability. Usually, sedation is needed for pain control, and for accuracy (the test is more accurate when your pet’s muscles are relaxed).
- X-rays to look for changes within the knee joint to help confirm an ACL tear. These changes may be subtle if it’s a recent injury, or there may be signs of arthritis and other chronic changes if the injury happened a while ago.
Is surgery necessary?
Every pet is an individual, so your veterinarian will talk to you about your options and determine whether or not surgery is the best option. This may include a consultation with a veterinary orthopedic surgeon, like our surgical director Dr. Amy Kantor, who specializes in treating this type of condition.
For most healthy pets, surgery is a good option because it stabilizes the knee joint to prevent pain, makes it easier to walk, prevents further joint damage, and slows down the development of arthritis.
While complications are possible with any surgery, the procedure for an ACL injury is very common (one of the most common procedures a veterinary orthopedic surgeon performs), and many pets have an increased quality of life after the procedure.
What does the surgery entail?
Common options for stabilizing the knee joint following an ACL tear are surgical procedures called TPLO (tibial plateau leveling osteotomy) and TTA (tibial tuberosity advancement).
The names are a mouthful, but the important thing to know is this: These procedures involve realignment of the tip of the tibia (the shin bone) at an angle that prevents the bone from sliding forward — and this realignment stabilizes the knee joint. The change is permanent thanks to a sturdy bone plate (a metal implant).
On the day of surgery, you’ll bring your pet to the clinic fasted, and the procedure will be performed by our surgeon.
Some pets may stay in the hospital 1-2 days after the procedure, for intravenous pain medication, monitoring, and to help with assisted mobility and exercise restriction, so your dog doesn’t overexert themselves too soon after the procedure.
What is lateral suture?
At Bond Vet, our surgeon Dr. Amy Kantor, performs lateral suture surgery for ACL tears. It involves surgically placing a very sturdy suture (the type of material used for stitches) on the side of the knee joint to act as an “artificial ligament.”
Alternative common procedures for ACL tears are TPLO (tibial plateau leveling osteotomy) and TTA (tibial tuberosity advancement), which involves realignment of the tip of the tibia (the shin bone) at an angle that prevents the bone from sliding forward, which stabilizes the knee joint.
What does recovery look like?
When your pet comes home, they’ll probably receive
- Pet-safe medications for pain and inflammation.
- An Elizabethan collar to prevent licking and chewing of the incision site.
- A bandage over the leg.
Usually, the most difficult part of recovery is encouraging your pet to rest. Too much physical activity too quickly can have a negative impact on healing—and yet, your pet will probably want to play as soon as they feel better, because they don’t understand that they’re still healing and need to rest their leg.
Full recovery takes several weeks, and your vet will give you instructions on how soon and how quickly to start increasing your pet’s physical activity, as well as when to schedule a recheck.
Your individual pet’s instructions may vary, so always follow your vet’s instructions exactly, and call your vet’s office with any questions or concerns.