Dog ACL Tear (Cranial Cruciate Ligament Tear)

If you suspect your dog has a torn cruciate ligament or your veterinarian has diagnosed it, you’re not alone. Torn ACL in dogs are hands down the most common orthopedic injury in dogs. In fact, it has been reported that 85% of all orthopedic injuries in dogs are some form of ACL injury.

So what exactly does this injury in your dog entail, and what can you do about it? Here’s everything you need to know about ACL tears in dogs, treatment options, and how you can help your pet on the road to recovery.

What Is It?

An ACL tear in dogs is a knee injury that occurs when a dog fully or partially tears their cruciate ligament. Before we go any further, it’s important to note that “dog ACL tear” is a term commonly used for this type of injury, although your veterinarian will likely refer to it as “cranial cruciate rupture.” To keep things simple, we’ll use the term “dog ACL tear.”

In order to fully understand this injury, it helps to have a basic understanding of the anatomy of a dog’s knee. The knee often referred to as the “stifle” by veterinarians, is the joint in between the femur and the tibia in the hind leg.

Inside of this joint, there is cartilage, joint fluid, two menisci, and of course the dog cruciate ligaments, of which there are two of them crisscross. These crisscross cruciate ligaments provide much of the knees stability and are responsible for keeping the tibia from sliding too far forward, or too far backward when the dog bends their knee.

When a dog tears its ACL, every time they go to stand or put weight on their injured leg, the femur slides on the back of the tibia. This rubbing causes pain and inflammation, which is extremely uncomfortable for your beloved pet.

It’s important to understand: Dog ACL tears are classified as either partial tears or complete tears. It is crucial that you have a veterinarian determine the degree of injury to your dog’s knee, which will provide more insight into the best solution for treatment and recovery.

In addition, it’s also important to know that due to the instability this ACL injury creates in your dog’s joint, it’s also one of the main causes of degenerative joint disease (DJD), more commonly known as arthritis in dogs.

Click Here to Download Your Free Guide to Cruciate Surgery & Recovery: Recommended by Top Orthopedic Veterinary Surgeons

Why Do Dogs Injure Their ACL?

All dogs are at potential risk of tearing their ACL. According to research, no one particular age, gender, or breed of dog has been pinpointed as being most at risk. That said, the most commonly reported dogs with ACL injuries are young, active, large-breed dogs, such as Mastiffs, Labrador Retrievers, Rottweilers, and German Shepherds to name a few, but small dogs can sustain ACL injuries as well.

Additionally, overweight dogs are at greater risk of rupturing their ACL ligament than healthy, well-conditioned dogs.

The vast majority of ACL injuries in dogs are a result of hyperextension of the knee joint, aka when the knee is thrust forward and forced to extend beyond its normal range of motion. This is why in humans, the most common people who blow their ACL are football players or basketball players, because they are continually “thrusting forward” i.e. hyperextension. Some of the more common scenarios reported from dog owners revolve around the dog chasing a squirrel in the backyard or playing hard with a friend.

Why So Many Dogs Tear Their ACL:

  1. Lack of Daily Exercise
  2. The Vast Majority of Dogs are Overweight
  3. Dogs knees are always bent therefore there is constant tension on the dog ACL ligament
  4. Weekend Warrior Syndrome
  5. Bad Breeding and Hip Dysplasia
  6. Lack of recognizing early warning signs

What is most important though is how to prevent the same injury to your dog’s OTHER hind leg. We will touch on this in a later section.

Click Here to Download Your Free Guide to Cruciate Surgery & Recovery: Recommended by Top Orthopedic Veterinary Surgeons

What Are The Signs?

Pet owners often report hearing their dog “yelp” in pain and then start limping after their dog injures the ACL. But in many cases, the pet owner never hears any cry and all of the sudden notices their dog limping or not putting any weight on the hind leg.

Here are some simple guidelines to follow:

  1. If your dog is not putting any weight on the hind leg and is holding it up, then there is a very good chance they may have a FULL tear of their ACL.
  2. On the other hand, if your dog is just slightly limping or using the leg but not putting full weight on it, then there is a good chance they may have a PARTIAL tear of their ACL.

How Is It Diagnosed?

For the best diagnosis, it is imperative that you seek the advice of a veterinarian who is familiar with diagnosing dog ACL injuries. Diagnosis is based on the demonstration of a specific test, called the cranial drawer test. This is best performed with the dog lying on its side in a relaxed state. Because it is so important that the dog is relaxed in many cases slight anesthesia or sedation is need for the best results. Your veterinarian will perform a proven test to determine if an ACL tear is the source of your dog’s pain and if the tear is partial or full. This is crucial information when moving forward with a recovery plan.

Cranial Drawer Test:

The examining veterinarian positions their thumb and forefinger of one hand on the femur, and the other hand is placed on the tibia. The femur is held in place while the other hand shifts the tibia backward and forward.

In a normal, stable joint, there will be little to no motion ie. instability. The rupture of the cranial cruciate ligament allows the tibia to slide forward. Therefore, a positive cranial drawer test is indicative of cruciate ligament damage.

Tibial Compression Test:

Another test that is used to diagnose dog ACL injuries is the tibial compression test. In this assessment, one hand is placed around the end of the femur, with the index finger extended over the patella. The other hand grasps the foot and flexes the hock (ankle). If the tibia moves forward, it is an indication of ACL damage.

Other Diagnostic Options:

Another valuable test is to have radiographs ie. x-rays taken of the knees and the hips. This is a great way to rule out other causes of lameness such as fractures or hip problems. In addition, x-rays will also show any signs of arthritis.

A more elaborate and advanced form of diagnosis would be arthroscopy, in which a small camera is used to look inside of the joint and see the degree of damage.

Click Here to Download Your Free Guide to Cruciate Surgery & Recovery: Recommended by Top Orthopedic Veterinary Surgeons

How Is It Treated?

Dog ACL tears or cranial cruciate ligament ruptures can be treated either surgically or medically (i.e. rest, physical therapy, etc.). It’s important to understand these simple guidelines:

  1. All FULL ACL tears require surgery for the best results. The simple reality is that the knee needs to be stabilized via surgical operations in order to be functional.
  2. Depending on the degree of the PARTIAL ACL tear and/or the size of the dog, some partials tears can be treated successfully with medical management utilizing modalities such as rest, physical therapy, cold laser therapy, and joint supplements, to name a few.

In general, surgical stabilization is recommended in all patients with ACL tears, both full tears and partial tears that are compromised greater than 50%.

Surgical Options:

There are a number of surgical techniques to choose from. Your veterinarian can help you decide which surgical procedure is best for your dog, based on these considerations:

  1. Severity of the injury
  2. Size of the dog
  3. Age of the dog
  4. Lifestyle activities
  5. Financial considerations etc.

Here are the three most common recommended surgeries with basic descriptions of each. For a more complete understanding of each surgery follow the links to the TopDog Orthopedic Surgery Library. Each surgery page has photos and diagrams to help you understand the entire process.

  1. Extracapsular Repair/Lateral Suture Repair/Lateral Fabellar Technique: This surgical procedure actually has a number of different names – we’ve listed the most common ones. The surgery involves the placement of a monofilament suture (similar to fishing line) outside of the joint. The suture is passed around the small bone (the lateral fabella) on the backside of the femur and then passed through a hole drilled in the top of the tibia. The sutures are placed in a way that mimics the normal anatomic orientation as your dog’s ACL ligament. The sutures are then tightened appropriately to stabilize the joint without making it too tight. The key to this surgery is in the formation of scar tissue in the first 8 weeks after surgery. This procedure is more commonly recommended for small dogs and cats or pet owners with financial considerationsFollowing surgery, physical therapy is recommended to help in the healing process, in regaining normal joint function, and in maintaining muscle tone
  2. Tibial Tuberosity Advancement (TTA): This surgery is one of the procedures indicated for medium and large breed dogs with ACL injuries. This technique involves making a cut in the front part of the tibia, called the tibial tuberosity. The cut portion of bone is advanced forward in order to realign the patellar ligament, and a bone spacer, plate, and screw are used to secure the new position of the bone. This procedure eliminates the abnormal sliding forward within the joint. Then bone graft collected from the top of the tibia is placed in the space so that new bone growth fills it in and stimulates healing. Following surgery, physical therapy is recommended to help in the healing process, in regaining normal joint function, and in maintaining muscle tone
  3. Tibial Plateau Leveling Osteotomy (TPLO): Now one of the most popular surgeries performed to repair torn ACLs in dogs, the TPLO is generally recommended for larger dogs, and those with a steep slope of the tibia, regardless of size. This procedure involves removing the torn ends of the ligament, and any parts of the meniscus that are damaged. Then a curved cut is made in the top of the tibia, and the tibial plateau is rotated so that the slope is leveled out. The repositioned bone is held in place with plates and screws. Following surgery, physical therapy is recommended to help in the healing process, in regaining normal joint function, and in maintaining muscle tone.

Can It Be Prevented?

Unfortunately, there is no sure-fire way to prevent ACL injuries in dogs. As we mentioned, research has not pinpointed one particular age, gender, or breed of dog that is most at risk for an ACL injury, but there are steps you can take to help avoid this injury in your dog.

Here are TopDog’s top tips to prevent an ACL tear in your dog:

  • Give Your Dog Daily Exercise – If your dog isn’t receiving regular exercise, the ligaments and surrounding muscles of their knee are not being kept strong and healthy. Make sure your dog gets some form of exercise every day.
  • Keep Your Dog at a Healthy Weight – The more weight your dog is carrying, the more stress and strain on their knees. Feed them a healthy diet, avoid overfeeding, and provide regular exercise.
  • Give Your Dog a High-Quality Joint Supplement – Prevention, prevention, prevention. Even if your dog is not yet showing signs of joint issues, a quality joint supplement will provide them with the essential nutrients to keep their joints strong and healthy
  • Avoid Weekend Warrior Syndrome – If your dog is lying around all week when you’re at work, then going extra hard on the weekends, this is a recipe for a torn ACL. Regular, moderate exercise is better than infrequent overexertion.
  • Avoid Excessive High Jumping – There’s a reason so many basketball players tear their ACL. Hyperextension of the knee can occur when your dog lands wrong after a jump, so it’s best to avoid excessive high jumping.

How Can I Prevent Another ACL Tear in My Dog’s OTHER Knee?

If your dog does sustain an ACL injury, it’s extremely important to take steps to prevent the same injury to your dog’s other hind leg.

Listen very closely: Since your dog has injured one hind leg, they are having to compensate on their three other “good” legs. This compensation puts their other legs, back, and joints at greater risk of injury. It is estimated that 30-50% of dogs who tear one ACL will tear the other ACL within a few years.

The reason for this is very simple: lack of physical therapy and proper conditioning after surgery and lack of good joint health supplements. It is as simple as that.

So what can you, the pet parent, do to help?

Step 1: Take an active role in your dog’s recovery process.

Here at TopDog Health, we’ve created informative step-by-step guides to help pet owners like yourself learn the essentials on how you can best help your dog through the entire process of recovering from an ACL injury. This free guide details the numerous (and simple!) therapies and exercises you can do right in the comfort of your home to help decrease your dog’s pain and improve their chances of a successful, lasting recovery.

Step 2: Provide your dog with the essential nutrients their joints need to fully recover and stay healthy, i.e. a high-quality joint supplement.

It is never too late to start your dog on a quality joint supplement that will provide them with the essential nutrients to keep their joints strong and healthy. Starting and maintaining your dog on a joint supplement like GlycanAid HA which was developed for pre and post-surgical consumption will give your dog’s other leg a fighting chance. With the addition of Flexerna Omega, our potent natural anti-inflammatory your dog will be thanking you for years to come.

What Is The Prognosis For My Dog?

Early diagnosis and treatment is critical for improving the long term prognosis and will minimize the progression of Degenerative Joint Disease (DJD) or arthritis. The worst-case scenarios are the dogs who have a partial tear that goes undiagnosed for a long period of time. The chronic instability in the joints leads to arthritis and the compensation leads to potential injury to the other legs.

Though reported statistics vary, it is estimated that on average 30-50% of dogs who tear one ACL will tear the opposite ACL within a few years. As mentioned previously this is entirely due to compensation stress, which over time is a result of lack of proper post-surgery physical therapy and the proper use of joint health supplements which can make a huge difference in improving the overall health of the joints.

The reality is this: Once you decide the best treatment for your dog’s ACL injury and they have the surgery, there are two main steps you need to take to ensure a successful and lasting recovery:

Physical Therapy:

  • Download and follow TopDog’s FREE Home Rehabilitation Guide with essential therapies and exercises for strengthening
  • Locate and seek advice and services from a local canine rehabilitation specialist (Click Here to find a Canine Rehabilitation Facility in your area)

Joint Supplements:

  • Start your dog on an effective, high-quality joint supplement (TopDog’s Joint Supplement for Dogs, GlycanAid® HA, which was specifically designed for dogs after orthopedic surgery or dogs requiring the highest level of joint support). Adding in Flexerna Omega, a potent natural anti-inflammatory will help in the healing and overall health of your dog’s joints.


  • Understand that COMPLETE recovery takes on average 6 months and therefore DO NOT let your dog off-leash before they are ready

While ACL tears are an extremely common injury in dogs, successful recovery is just as common. If you take it upon yourself to get educated about your dog’s injury and what you can do to help with their recovery, your dog will do amazing – just like the thousands of others that TopDog Health has helped throughout the years.