The Cambria Dog’s ACL Injury

Injury to the Anterior Cruciate Ligament, or ACL, is the most common reason for hindlimb lameness in our dogs. It can be an acute injury caused by a misstep or fall, or it can be a chronic problem caused by gradual wear and tear in an overweight pet. But the bottom line is that it is a gamechanger for your pet and the way they lead their life. Because of this, it is important that you be as well educated as possible about why this happened, what can be done for it, and what this means to the future of your dog

The Anatomy of Your Dog’s Knee…

or, for that matter, ours… The bottom end of the thigh bone is round, and the top end of the shin bone is also round. This makes the knee inherently unstable, just like trying to balance two baseballs on top of one another. The only thing that makes this balancing act even possible is the X-shaped cruciate ligament. When the cruciate ligament is torn, the knee becomes very unstable, and severe pain and arthritis develop very rapidly.

The diagnosis of ACL injury…

Sometimes it’s easy, when your dog runs off normally and comes back carrying a hind leg. Other times it is more insidious, and all you know is that your dog can’t walk as far as they used to. In either case, we need to visit. When the Anterior Cruciate Ligament is torn, the thigh bone and shin bone can be moved in opposite directions simultaneously. An intact ACL will prevent this from happening. This examination must be performed under anesthesia to get adequate muscle relaxation. At the same time we get a set of radiographs of the knees and hips of your dog to fully evaluate their overall orthopedic condition.

The result of ACL rupture…

is severe, rapidly progressive pain and arthritis. This is because every time a dog bears weight without an intact ACL, the bones grate upon one another. As arthritis develops, the knee can become so painful that a dog will not bear weight on it. This creates a high likelihood of similar injury in the other knee.

Every Dog with Knee Problems should…
  • be kept as thin as possible for the rest of their life
  • be given glucosamine, chondroitin, curcumin, and fish oil daily
  • be given painkillers as required to keep comfortable
  • be given moderate exercise with good footing
  • avoid stairs and jumping
  • be loved and spoiled!!

Surgical Stabilization of the ACL-deficient knee…

The unfortunate truth is that any patient who has suffered a ruptured ACL will be best treated by the surgical exploration and restabilization of that knee. Unfortunately, we cannot simply repair the ACL, as it has no blood supply and thus would never heal. You can order various splints and braces over the internet, but I just have never seen them work. Our goals during such a procedure are to…

  1. remove all damaged tissue from the joint;
  2. assess and remove any torn joint cartilage;
  3. restabilize the knee using one of three different procedures.

You should be aware of the fact that any stabilization procedure will NOT return your dog to “normal”.

Rather, our goal is to minimize knee instability and the progression of painful arthritis, and thus offer your pet maximal quality of life. There are two components to the success of a surgical knee restabilization procedure. The first is the experience and skill of the surgeon you select to perform the desired procedure. The second is YOU AND YOUR AFTERCARE AT HOME. The aftercare recommendations vary with the type of surgery, patient, and surgeon, but in general they consist of…

  1. Oral antibiotics and painkillers for 3-7 days postoperatively;
  2. Incisional care– cleaning, preventing the patient from licking– until the sutures are removed in 14 days or so.
  3. Absolute confinement for 2-4 weeks, followed by gradually-lengthening leash walks for another month or so. There will likely be no off-leash exercise for at least 2 months.

The three different stabilization procedures we recommend are…

  • extracapsular repair
  • the new Tightrope procedure
  • TPLO (=tibial plateau leveling orthotomy)

… so let’s explore each of those options


This is the old standby restabilization, which was developed about 15 years ago. In essence, we use 1-2 strands of heavy surgical monofilament (think expensive fishing line) that are tunneled through the bones to mimic both the path and the function of the now failed ACL. The advantage to this form of restabilization is that it is the most economical on a relative basis ($1200-1500) and is well suited to dogs up to about 40 lbs or so, or for older/less active dogs. You should know that in most instances these stabilizing sutures eventually stretch or break, but this surgery’s high rate of success is due to the fact that in the interim scar tissue has formed within the joint, and this scar tissue keeps the joint stable even if the suture eventually fails. The other thing to remember is that, while our suture replaces the function of the old ACL, it does nothing to alter the “round on round” anatomy that led to the ACL’s progressive weakening in the first place, so we are essentially reinforcing the faulty conformation that created the instability in the first place.


… is the most recent improvement in restabilizing a dog’s knee. It is a specialized procedure performed here that can be used in any size dog and offers excellent results. While it is a little more expensive ($1800-2100), the results in our patients have been VERY good. The specialized suture that we use is much stronger and more durable than the monofilament above. The reason that the Tightrope works so well is because of a) better suture material, and b) extensive research showing the exact location of our bone tunnels so as to minimize not only joint instability but also force applied to our suture. While most experienced surgeons — including me– feel that the results offered by the Tightrope stabilization procedure have DRAMATICALLY improved postoperative comfort for our patients, again we are reinforcing the “round on round” anatomy that your dog was born with.


The TPLO procedure was developed about 12 years ago to address the “engineering” of the knee. Specifically, it changes the “round on round” anatomy I have mentioned as being an inciting cause for ACL rupture to a much more stable “round on flat” anatomy, like balancing a ball on a table rather than balancing a ball on another ball. The way this can be accomplished is by surgically CREATING a fracture in the top of the shin bone, rotating the top of the shin bone around, and placing a bone plate across the new fracture to keep it in place. If you saw a radiograph, you’ll understand better– so come on in and let’s talk!! The advantage to this procedure is that it DOES improve the original anatomy, and is thus well suited for young/athletic or large breed dogs. The disadvantages are that it is the most invasive procedure (ie, a larger incision needs to be made) and also that it is also more expensive, at $3200-4000 or so.

I hope that this webpage has given you a better idea of the reasons for your dog’s hindlimb discomfort and the alternatives that we have in maximizing your pet’s future quality of life. If you have additional questions I would be happy to sit down with you at any point in time and offer you my honest opinion about your concerns. Thank you again for bringing your pet to Cambria Veterinary Clinic. Let us know how we can help you –and we will!!