Dog ACL injuries
As Wally can attest, dog ACL injuries are all too common.

It’s a cold winter evening. My dogs go out for their last little romp before nestling snug in their beds.

Wally, the 11-year-old cocker spaniel, calmly walks up the two little steps to the deck, turns quickly to check on me, and turns his leg on the icy step.

A tiny yelp, barely audible in the quiet of the starlit night, and there goes his cruciate ligament.


Oops, there it is. A tiny yelp that could cost $3,000 to repair.

The most common orthopedic problem in our pet dogs is not broken bones or hip dysplasia. It’s the knee! Injury to the anterior cruciate ligament (ACL), also known as the cranial cruciate ligament (CCL), is all too common.

Knee injuries can be complicated to diagnose and to fix. There is controversy about when a dog needs surgery, and which surgical procedure is the best. When there’s controversy about how to solve a problem, like the best way to fix a dog knee, it usually means we don’t have all the answers, and this can frustrate owners. It frustrates me, too.

Add another factor to this mess: The cost. Surgery to repair a dog’s knee starts at expensive and can proceed to very expensive. Think anywhere from $1,500 to $4,000.

“Okay,” says the dedicated dog owner, “so I’ll cough up the bucks and then Chester’s knee will be fine, right? Oh, and what does he come home with? A cast or something? He’s good in about two weeks, right?”

Not so fast, Chester’s dad. Do you want the troublesome news or the bad news first? Chester’s knee has a good chance of being fine but it’s going to take a while. And no, the recovery is not a walk in the park, so to speak. Chester is going to be limited to very short walks in the park for several months.

And during that time, Chester’s overall activity has to be limited. He can’t do stairs or run free. You need to be willing to do some doggie physical therapy, or bring him to a canine rehab facility. After all that, any dog who blows out one cruciate has a 30 to 40 percent chance of tearing the ACL in the other knee some time down the road.

But Chester Just Tripped!

It doesn’t take much for your dog to sprain, partially tear or completely tear his cruciate ligament. He might jump off the bed and just land funny. She might walk up two front steps and trip. Maybe he jumps up for a frisbee, like he’s done 1,000 times before, but comes down wrong on the rear leg.

Or, maybe she took a walk by the stream and stumbled on a rock. Many times, the owner brings the dog in to me for what he thinks is a minor sprain, only to learn the upsetting news about dog ACL injuries.

Think of an ACL as a cable wire or a thick piece of twine. It is made up of many fibers. Sometimes the fibers are just stretched, strained or partially torn. Some dogs may improve if they have a slightly damaged cruciate ligament. Many, however, will continually limp on the leg, not be able to have a normal life and require surgery.

Risk Factors

  • Obesity. Fat dogs are more prone to knee injury. Listen to your vet and get your dog back to a normal weight.
  • Exercise. Dogs should have regular, daily exercise. If you want your dog to be more of an athlete, condition him as you would yourself. You wouldn’t run a marathon with no training. Neither should your dog.
  • The weekend warrior. Don’t let Elmo sleep on the couch all week and then let him run up Mt. Rainier on Sunday. Overdoing exercise with a dog that is not walking/running daily sets him up for injury, particularly knee injury.
  • Genetics and conformation. Even under ordinary circumstances, the dog’s knee is under more stress than the human counterpart, and is prone to injury more easily. Many ACL injuries in humans are athletic in nature, but the dog’s knee behaves like it’s on a basketball court in everyday life. In a human, it often takes a bad accident, like what Olympic skier Lindsey Vonn just endured. Now she has lots in common with Tiger Woods! Your pup doesn’t have to take to the slopes or the basketball court to sustain serious injury to his ACL.

Stifle What?

Dog ACL injury radiographThe knee is a complex joint. If you want to impress your friends, call it the stifle joint. There are two cruciate ligaments, two collateral ligaments, the lateral and the medial menisci, four bones and a knee cap (patellar).

Think of the cruciates as a crisscross of two bands holding your femur (top bone in your leg) to your tibia (lower bone). They rarely endanger the posterior cruciate ligament. When the ACL is torn, the entire leg is unstable, and the bones are rubbing, causing inflammation and degenerative joint changes.

By the way, our four-legged friends are like us with only two knees. Dogs’ front legs are built like our arms. This may sound like a no-brainer, but many dogs come in with an elbow injury and their owners think they’ve hurt “a knee.”


The best way to diagnose an injured knee is the good old fashioned way: the physical exam by your vet. A vet cannot always diagnose the exact nature or extent of the knee injury, but can give you guidance on how to proceed. If an ACL is completely torn, it is quite clear when your vet palpates the knee. There will be a back and forth movement in the knee called a “drawer” sign.

But to get more detailed info about the exact details of the injury, i.e., how many other structures are involved, etc., you need advanced imaging like MRIs or CTs. This is not usually practical for dogs, although we will probably be doing many more of these in the future as the technology becomes less expensive and more readily available.

Regular radiographs are usually taken to make sure there aren’t other significant changes in the knee or hip, but the exact damage to the ligaments in the knee do not show up on a regular radiograph.


The very first thing your vet will probably tell you is to severely limit your dog’s activity and prescribe rest. NSAIDs (non-steroidal anti-inflammatory drugs) are also usually prescribed.

If the vet did not find significant movement in the knee, swelling or pain, she or he may recommend a short period of rest to see if this is just a seriously sprained knee, with the caveat that many of these knees do not improve and will need surgery. If your dog is walking well on the knee within a week or so, clearly the ACL was not severely torn. If the limp continues without improvement, you need to follow up with your vet.

A small dog may do better with some ACL injuries without surgery, while a larger dog is most likely going to need surgical repair. I find most dogs thirty pounds or over require surgery.

Disclaimer: If the ACL is completely torn, even tiny dogs most likely need surgery, particularly if they’re active.

Surgical Repair

Here’s the part of the story I don’t like. There are at least three well-known surgeries commonly used to repair a cruciate ligament. They are all very different, and there are significant differences in cost.

Even though ACL tears are so common, and thousands upon thousands of surgeries have been done to repair dogs’ knees, there is still no clear consensus in the veterinary community as to which procedure is best for which dog.

Geometry, You Say? In a Knee?

There are three commonly used procedures to fix a knee:

  1. Lateral suture technique. This older, more common and still highly recommended repair consists of placing a synthetic suture in the knee to restore stability in place of the ACL. In the hands of a good surgeon, this surgery is recommended for many dogs, particularly dogs under fifty pounds.
  2. TPLO (tibial plateau leveling osteotomy). This is a referral orthopedic procedure. This surgery actually changes the conformation of the knee. The tibia is cut, moved and reattached. If done without complication, this surgery may result in less arthritic changes, and is often recommended for larger dogs.
  3. TTA (tibial tuberosity advancement). This surgery also requires a surgeon with specialized training. In this procedure, the tibia is cut and allowed to heal at a different angle, lessening the mechanical stresses on the knee. Both the TPLO and the TTA actually change the geometry of the knee joint. They are much more expensive than the lateral suture surgery, and require veterinary surgeons who are specially trained in the procedures.

Discussing these surgeries in detail is far beyond the scope of this article. Take-home message: Consider at least two opinions when your dog is diagnosed with an ACL injury, or ask your veterinarian if he or she is willing to talk in depth about ALL options available to you.

Beware: I think some surgeons go straight for the more involved procedures when this may not always be your best or only option. Get as much information as you can based on your particular dog, and the specific injury.


Wally, on the road to recovery
Wally, on the road to recovery

Recovery is slow, with physical therapy done by you, or with the help of a trained canine rehabilitator.

If you have some money left over after surgery, and the time to go to some rehab appointments with your dog, professional rehabilitation is great. The fact that our pets need PT after trauma or surgery seems like a no-brainer, but it is a fairly new field in veterinary medicine. We will be doing more and more of it.

There is a lot of information on the internet suggesting dogs with ACL injuries don’t need surgery. The claim is they just need physical therapy. Although dogs with incomplete tears, smaller dogs and dogs that don’t do much in life can benefit from weight loss and physical therapy, I think these claims are misleading.

Many dogs limp continuously with a knee injury, never improving with conservative treatment, or their condition worsens. If surgery should be done and is not performed, the dog can suffer arthritic changes to the knee, the hip and the other leg. This is a painful situation that also limits his life as a happy, frolicking dog.

We are seven weeks post-op Wally’s ACL surgery and he is doing great. Walking him under icy conditions this winter, and carrying him up a long flight of stairs at night, has not been easy, but it’s been worth it.

He is slowly getting back to his old routines, tolerating his physical therapy every day, and should be back to normal by spring. Hats off to his surgeon (not me), his owner (me) and to Wally!

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