The Canine Ledger

Cruciate Ligament Rupture: Surgery, Conservative Care, and the Evidence Gap

A torn cruciate is the classic sudden back-leg limp. What the one trial of surgery versus no surgery found, and which operation has the most support.

Written by thecanineledger

In a randomised trial of 40 overweight dogs with a torn cruciate ligament, surgery gave better results. But “almost two-thirds of the dogs in the nonsurgical treatment group had a successful outcome at the 52-week evaluation time” (Wucherer et al., Journal of the American Veterinary Medical Association 2013, abstract).

That is the only randomised trial of surgery against no surgery that we found. It is the most important study an owner facing this decision can read, and it is rarely mentioned.

While surgery is the usual recommendation, and the evidence favours it for most dogs, the evidence base is far thinner than the confidence of most recommendations suggests. This page sets out what is known about the injury, what the studies of surgery and conservative care show, and which questions they leave open.

1. What it is, and which dogs get it

The cranial cruciate ligament sits inside the knee (stifle) and stops the shin bone sliding forward. It is the dog’s version of the human anterior cruciate ligament.

In dogs, it usually wears out rather than snaps. The Merck Veterinary Manual’s owner page explains that while a tear is “a very common injury in dogs”, “injuries are more likely to occur when the joint structure is already weakened by degeneration, the animal’s own immune system, or defects in conformation (such as those seen in straight-legged dogs)” (Merck, Other Joint Disorders in Dogs).

How common is it? A study of 171,522 dogs at English primary-care practices put the prevalence of a cruciate diagnosis at 0.56% (Taylor-Brown et al., Veterinary Surgery 2015, abstract). Compared with crossbreds, these breeds had higher odds:

  • Rottweilers
  • West Highland White Terriers
  • Golden Retrievers
  • Yorkshire Terriers
  • Staffordshire Bull Terriers

Heavier dogs within a breed, dogs over three, and neutered females (“2.1 times the odds of diagnosis compared with entire females”) were also at higher odds.

→ When to Spay or Neuter: What the Breed Studies Show, and What They Don’t · → Choosing a Breed or a Mix: The Health Data Breeders Don’t Lead With

2. The signs

Merck lists “lameness, pain, joint swelling, fluid buildup, and a grating sound when the joint is moved”, and notes that “the joint may appear to be abnormally loose.” Partial tears reduce the knee’s ability to bend.

The typical story is a dog who is suddenly lame on a back leg, often after running or jumping, and may touch only the toe to the ground. Some dogs have a milder limp that comes and goes.

When to see a vet. A dog who won’t put any weight on a leg, or is in obvious pain, should be seen the same day. A milder limp that lasts more than a day or two should be checked, because other conditions can look similar and a partial tear can progress.

Our note: The “typical story” paragraph and the “when to see a vet” lines are ours. If your dog won’t bear weight, see a vet the same day.

→ Emergency Signs in Dogs: When to Go Now, Not Tomorrow

3. Surgery or conservative care?

Merck describes both: “Physical therapy, weight reduction, and nonsteroidal anti-inflammatory drugs ease discomfort from inflammation and degenerative joint disease. For active dogs, surgery to stabilize the knee joint is recommended.”

The one trial. In the Wucherer trial, 40 overweight dogs with a tear in one knee were randomly assigned to conservative care (physical therapy, weight loss and an anti-inflammatory) or the same care plus surgery (a TPLO, described below). Success meant the affected leg pushed on a force plate with more than 85% of the force a healthy dog’s leg does, plus at least a 10% improvement in the owner questionnaire.

Weeks after startingSuccessful outcome, surgerySuccessful outcome, no surgery
1267.7%47.1%
2492.6%33.3%
5275.0%63.6%

The authors’ conclusion: dogs given surgery plus conservative care “had better outcomes than dogs treated via nonsurgical methods alone.” But most of the conservatively managed dogs did well by a year.

What it can’t tell you. It was 40 dogs, all overweight, with one knee affected, followed for a year. It does not tell you what happens over five years, in lean dogs, in very large or very small dogs, or in dogs with both knees affected.

Our note: We found no study we could read on whether small dogs do fine without surgery.

What happens in practice. In the English primary-care study, “Two-thirds of cases were managed surgically, with insured and heavier dogs more frequently undergoing surgery.” Insured dogs also had “4 times the odds of diagnosis compared with uninsured dogs”. That says as much about which dogs reach a vet and get investigated as it does about the knee.

Our note: Our reading is that the insurance finding reflects which dogs get diagnosed and treated, not a higher risk of injury. The abstract doesn’t interpret it.

→ How Pet Insurance Works: Policy Types, Excess, Co-Insurance and Waiting Periods

4. Which operation?

There are several. The three most studied are:

  • TPLO (tibial plateau levelling osteotomy): the top of the shin bone is cut and rotated to change the angle of the joint, then fixed with a plate.
  • TTA (tibial tuberosity advancement): a different cut moves the front of the shin bone forward.
  • Lateral suture (extracapsular repair): a strong suture outside the joint takes over the ligament’s job, with no bone cut.

The 2014 systematic review. It found 34 qualifying studies and concluded that “The strength of the evaluated evidence most strongly supports the ability of the TPLO in the ability to return dogs to normal function.” It also found “strong support that functional recovery in the intermediate postoperative time period was superior following TPLO compared with lateral extracapsular suture.” For other procedures, “There was insufficient data” (Bergh et al., Journal of the American Animal Hospital Association 2014, abstract).

The 2022 review, TPLO against TTA. It assessed 72 studies, and found that “Almost half (47.2 %) of the studies were considered of low quality of evidence.” Both operations were “considered to be successful management options”. TTA appeared to give better arthritis scores up to six months, and TPLO had fewer wound infections. Its conclusion: “no method can be clearly preferred, as most of the study evaluated were subpar” (Wemmers et al., Frontiers in Veterinary Science 2022).

What that means for you. TPLO has the most supporting evidence, and that is why it is so widely recommended. But the reviewers who looked hardest at the studies say the quality is poor. If your vet or surgeon recommends a particular operation, it is reasonable to ask why that one, for your dog, and what their own results are.

Our note: Asking a surgeon about their own results is a reasonable question for any operation.

After surgery, rehabilitation matters. Merck: “Physical therapy following surgery is critical for recovery. The outlook after surgery is good as long as degenerative joint disease has not progressed too far.”

5. Conservative care, done properly

If you and your vet choose conservative care, it is a treatment, not doing nothing. In the trial, it meant three things together:

  • Weight loss. Both groups lost body fat during the trial.
  • Physical therapy, usually guided by a vet or a qualified rehabilitation practitioner.
  • Anti-inflammatory pain relief, prescribed by your vet. We don’t name drugs or doses.

→ Ibuprofen, Paracetamol and Other Human Painkillers

Arthritis develops in a knee with a torn cruciate whichever route you choose. Merck notes that the instability “can lead to cartilage injury, buildup of joint fluid, bony outgrowths, and hardening and thickening of the joint membrane.”

→ Fish Oil for Arthritis: What the Trials Show

6. What we could not verify

Commonly saidWhat we found
“Without surgery, your dog will never walk properly again”Contradicted by the one trial we found. Almost two-thirds of overweight dogs managed without surgery had a successful outcome at a year.
“TPLO is proven to be the best operation”It has the most support, but a 2022 review said no method can be clearly preferred, because most studies were poor.
“Small dogs never need surgery”We found no study that tests this.
“A knee brace works as well as surgery”We found no study comparing them in the sources we read.
“Half of dogs will tear the other knee”Between about a fifth and a half, depending on the study. In one study of 85 dogs, 33% tore the other knee during follow-up. Its authors cite earlier figures of 22% to 54% (Chuang et al., PLOS ONE 2014). Ask your vet about your dog’s risk.
“It’s a sudden sports injury”Usually not. Merck describes a ligament already weakened by degeneration.

Sources

Always confirm with your vet before acting on anything on this page.