You've probably heard of sports players tearing their ACLs and needing to sit out from quite a few games. But did you know this knee injury is prevalent in dogs and even cats? In fact, ACL injuries are one of the most common type of orthopedic injury that veterinarians see in dogs. This guide will help you potentially recognize the symptoms of a torn ACL in your pup, and better understand the treatment options that can help your pet return to a happy, healthy life.
What does the ACL do?
ACL is short for Anterior Cruciate Ligament. In dogs and cats, veterinarians technically refer to it as the Cranial Cruciate Ligament (or CCL). The dog's ACL is found in the knee and consists of the cranial and caudal ligaments, which join the tibia (shin) and femur (thigh) bones.1 These two ligaments cross each other like an X, which allows the knee to act like a hinge. Having both ligaments intact is crucial to stabilize the knee, ensuring proper movement.
What happens when the ACL is injured?
ACL disease is a complex condition that can have multiple factors contributing to it. In people, the majority of ACL injuries are due to trauma, but in dogs, there are more factors at play. The majority of ACL ruptures are due to a degenerative condition within the knee that is sometimes compounded by trauma.
For example, a dog might be running and change direction fast, tearing the ligaments.1 An obese or older dog with degenerative changes in the ligaments might get the injury from a more minor movement, like simply stumbling.
Occasionally an ACL tear may start out with an incomplete tear, leaving your dog with a slight limp, and progress to a complete rupture, whereby the limp becomes more pronounced.
Torn ACL symptoms in dogs
Unfortunately, an ACL injury in dogs is very painful. You may notice your dog limping. If it's a partial tear, she might still try to bear some weight on the leg, whereas dogs with a complete tear will often opt to walk on three legs.2
Your dog might sit strangely, with the injured leg stiffly off to the side.2 He may have problems standing or jumping. Occasionally dogs with an ACL rupture will hold the toes on the injured leg slightly inward when standing. You may notice swelling on the inside of the knee. If left untreated, you may notice muscle atrophy in thigh muscles as he continues to bear less weight on the painful leg.
Of course, you'll want to check for less serious causes for lameness, such as cuts or something injuring the paw like glass or thorns. However, if you can't see an obvious cause for the discomfort or the lameness doesn't improve with rest, take your dog to the veterinarian.
How can you help prevent ACL injuries?
While humans tend to injure their ACLs through a traumatic injury, that is a less common cause for dogs. Of course, some athletic dogs can injure their knees during activity. But more commonly, it's the result of degeneration of the components of the knee over time and genetic predisposition.
Obesity can put your dog at greater risk of tearing an ACL. Keeping your pup at a healthy weight is important for decreasing load and stress on the knee joint. In one study, obesity quadrupled the risk of ACL rupture. 3
Some dog breeds are more likely to injure their ACL and require surgery. The ten breeds with the highest odds of tearing an ACL include the:
- Newfoundland
- Rottweiler
- Labrador retriever
- Boxer
- Chow Chow
- American Staffordshire terrier
- St. Bernard
- Alaskan malamute
- Airedale terrier
Larger dogs in general are also more prone to ACL issues.4
Your veterinarian can identify early risk factors that may make your dog more prone to an ACL tear. They may be able to diagnose a partial tear and suggest ways to keep it from becoming complete. Unfortunately, 30% to 40% of dogs with an ACL tear will develop a similar issue in the other knee. Insuring your dog when they are young can help reduce the chances of a condition being considered pre-existing so you'll have coverage when you need it!
How is an ACL injury diagnosed?
Only a veterinarian can diagnose an ACL injury.2 Your veterinarian will likely watch how your dog walks and palpate the knee, looking for instability. X-rays are commonly taken, even though soft tissue structures, such as ligaments, don't show up well. Radiographs don't reveal if the ligament is torn, but they'll confirm other signs, like fluid buildup and forward displacement of the shin bone, both can happen concurrently with an ACL tear. X-rays can also help rule out other underlying bone diseases. Sometimes MRIs or other advanced imaging modalities may be needed.
Dog ACL surgery and other treatments
There are different ways to treat an ACL injury, including several types of surgeries. The surgical management of ACL disease is of the more hotly debated topics discussed amongst veterinary orthopedic surgeons. There is currently no uniformly accepted gold standard treatment for this condition and following the recommendation of your veterinarian is best!5
1. Cage rest and pain relief
Non-surgical intervention is typically only worth trying in dogs that weigh less than 15 pounds, or in those patients where anesthesia is very risky. It can involve cage rest, weight loss and pain relievers. But this method when used alone doesn't see as great of success as other treatment options.
Rehabilitation is typically used to help speed recovery after surgery, but there's not a lot of evidence that it helps before or without surgery.2
2. ACL braces for dogs
ACL braces are another option for dogs, but these tend to be a short-term solution at best. They can be difficult to put on and keep on, and don't always provide enough stability. However, they can be a good option after surgery.
3. Lateral Stabilizing ACL surgery
One of the more common forms of dog ACL surgery for an ACL injury in smaller dogs (less than 25 to 30 pounds) is a Lateral Stabilizing procedure (also called an extra-capsular repair, "Fishing Line" or "Tight Rope" procedure.) It involves using a synthetic suture outside the joint, mimicking the torn ligament.6 The procedure generally accomplishes this only temporarily. The hope is that the suture remains viable long enough to allow for periarticular scarring to occur and create enough scar tissue to support the joint. 7
Theories have suggested that temporary stability through an extracapsular or lateral suture allows muscular rehabilitation sufficient to support the joint.8 Small dogs that already have arthritis or are older and less active may be better candidates for this surgery.9
4. Tibial Plateau Leveling Osteotomy (TPLO)
Tibial Plateau Leveling Osteotomy (TPLO) is a surgery that tends to be better for larger dogs. It involves changing the slope of the shinbone rather than replacing the ACL, giving the upper thigh bone a better surface to rest on.3 This has a better success rate with larger dogs than the lateral stabilizing procedure.
TPLO is also better for active dogs who have a tougher time resting while they're recovering. Both surgeries require rest, but the lateral stabilizing procedure requires more intensive, longer rest.9 Pets who undergo TPLO are typically given a little more freedom while they recover than pets who have the lateral stabilizing procedure.
5. Tibial Tuberosity Advancement (TTA)
Tibial Tuberosity Advancement (TTA) also changes the biomechanics of the knee, like TPLO, without replacing the ACL. The shin bone is cut, moved forward and a titanium cage is put in the cut.6 This tends to have a better success rate with larger dogs than the Lateral Stabilizing procedure. It can also be a good choice for active pets.
6. Cora-Based Leveling Osteotomy (CBLO)
Cora-Based Leveling Osteotomy (CBLO) is yet another way of changing the slope and mechanics of the knee. This procedure also levels the shinbone, but with a slightly different technique.
With any surgery, you may wonder if the pins and other hardware should be removed later. Typically, the hardware will stay unless your dog has some kind of issue or infection later.
How much does a dog's torn ACL injury cost?
An ACL injury always requires some upfront costs, including X-rays and an initial exam. After that, the cost depends on the treatment, your location, the dog's age, size and other factors. But whatever route you go, a cruciate ligament injury in dogs will always be expensive without insurance.
The lateral stabilizing procedure—the least costly of the surgeries—can run up to $2,300 or more. More advanced surgical repair with TPLO, TTAs and CBLOs generally costs about twice as much as lateral stabilizing surgery.9 The price can range from $2,500 to $6,000.10
Can a dog recover from an ACL injury without surgery?
Only about 20% of dogs over 30 pounds respond to non-surgical interventions like cage rest and pain relief.11 But about 85% of dogs that weigh 30 pounds will respond to non-surgical interventions and recover from a torn ACL in about four months.12 Your veterinarian will help you decide if surgery is necessary.
What happens if an ACL injury isn't treated?
Although some lighter-weight dogs may heal without surgery if put on strict cage rest, most will eventually need surgery at some point.1 In general, dogs have a better quality of life and less pain if they get some type of surgery, rather than no surgery at all.3 This is why your veterinarian will likely advise you to consider surgical interventions.
ACL injuries in dogs (and cats) should be taken seriously. They can be painful and limit the activities and playtime your pet can enjoy. The good news is that with surgical treatment, most pets can enjoy significant improvement and return to enjoying a happy, healthy life.
From Pets Best
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Sources
1Hunter, Tammy. Cruciate Ligament Rupture in Dogs. VCA. Retrieved from https://vcahospitals.com/know-your-pet/cruciate-ligament-rupture-in-dogs.
2Canine Cruciate Ligament Injury. Colorado State University. Retrieved from https://vetmedbiosci.colostate.edu/vth/services/orthopedic-medicine/canine-cruciate-ligament-injury/.
3Duval J M, Budsberg S C, Flo G L, et al: Breed, sex, and body weight as risk factors for rupture of the cranial cruciate ligament in young dogs. J Am Vet Med Assoc 1999 Vol 215 (6) pp. 811-4.
4Witsberger T H, Villamil J A, Schultz L G, et al: Prevalence of and risk factors for hip dysplasia and cranial cruciate ligament deficiency in dogs. J Am Vet Med Assoc 2008 Vol 232 (12) pp. 1818-24.
5Kim S E, Pozzi A, Banks S A, et al: Effect of tibial plateau leveling osteotomy on femorotibial contact mechanics and stifle kinematics. Vet Surg 2009 Vol 38 (1) pp. 23-32.
6Dog ACL/CCL Surgeries. Rice Lake Animal Hospital. Retrieved from https://www.ricelakeanimalhospital.com/dog-acl-surgery.phtml.
7Casale S A, McCarthy R J: Complications associated with lateral fabellotibial suture surgery for cranial cruciate ligament injury in dogs: 363 cases (1997-2005). J Am Vet Med Assoc 2009 Vol 234 (2) pp. 229-35.
8Hart R C, Hulse D A, Slater M E: Contribution of Periarticular Tissue to Stabilization of the Canine Stifle Joint After Cranial Cruciate Ligament Reconstruction. Vet Comp Orthop Traumatol, 27 Refs ed. 2003 Vol 6 (1) pp. 21-25.
9Anterior Cruciate Ligament (ACL) Rupture. Sunnyside Veterinary Clinic. Retrieved from https://www.sunnysidevetclinic.com/acl.
10Leicht, Kelsey. (2022, April 25.) ACL Surgery in Dogs: Costs & Healing Treatments. K9 of Mine. Retrieved from https://www.k9ofmine.com/dog-acl-surgery-cost-treatment/.
11RM Jerram & AM Walker (2003) Cranial cruciate ligament injury in the dog: pathophysiology, diagnosis and treatment, New Zealand Veterinary Journal, 51:4, 149-158, DOI: 10.1080/00480169.2003.36357.
12Wuchere K, Conzemius M, Evans R et al. Short-term and long-term outcomes for overweight dogs with cranial cruciate ligament rupture treated surgically or nonsurgically. JAVMA 2013: 242(10): 1364-1372.