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He's Got A Bum Leg, Doc
ACL Rupture in Dogs
Picture this: It is a beautiful spring day. You are playing fetch with your dog "Rascal" in the park or perhaps taking a walk through Moseley. Suddenly, Rascal takes off after a squirrel! Foolish dog, you yell for him to come back and when he does return, he is limping on a hind leg. Ok, you think to yourself, he did something stupid and now he sprained his leg. No big deal. A few days pass, Rascal is still limping, but is otherwise happy. The limping might come and go, but is overall pretty consistent. Now, you're a little worried and schedule an appointment for your veterinarian to check it out. At the appointment, your vet looks Rascal over and diagnoses an ACL tear! Oh, no!
What's an ACL tear, you ask. Isn't that something football players get? Your veterinarian explains that the ACL (anterior cruciate ligament), otherwise known as the CrCL (cranial cruciate ligament), is a ligament in the stifle or knee joint. There are actually two cruciate ligaments in the stifle. The cranial and caudal cruciate ligaments cross the joint from front to back and are named for where the lower part attaches to the femur (front or back). These two little ligaments play a major role in the biomechanics of the joint. When a dog ruptures his ACL, the stifle becomes destabilized, leading initially to lameness, pain and swelling in the joint. Here is a link to a picture of a normal stifle joint with the cruciate ligament labeled.
The history for a dog with an ACL rupture is fairly non-descript but classic. We see two common scenarios. In one, a typically young dog will present with an acute lameness in a hind leg. The lameness may initially improve with rest or NSAIDs, but will never go away completely. You may notice your dog limping more after exercise or first thing in the morning. In this scenario, the ACL is torn abruptly and the dog is acutely painful. But with time, the pain and inflammation decrease, making the dog a little more comfortable, but because of the instability in the joint, the lameness never resolves. In the second scenario, a dog will present with a lameness that comes and goes. It may seem to get worse over time. These dogs are typically older and in these cases, the ACL has weakened or stretched over time until it breaks down completely. Sometimes these dogs are diagnosed with "partial tears" since the ACL is still somewhat intact. This scenario is more of a degenerative process versus an injury, although some orthopedic specialists believe all ACL ruptures are inherently degenerative in nature. On rare occasions, we do see cats with an ACL rupture. These are almost always traumatic in origin, but diagnosis and treatment are very similar.
Diagnosis is generally straightforward. The instability in the joint can be demonstrated with a "drawer movement" that is not found in a normal stifle. Holding the femur steady, the veterinarian will manipulate the tibia. If the tibia moves forward abnormally like a drawer being open, the ACL is torn. Sometimes, a drawer movement cannot be appreciated because the dog is too tense or painful, so we often need to sedate dogs to truly diagnose an ACL tear. Checking for "tibial thrust" can also help diagnosis a rupture. Longstanding ACL ruptures will also cause a "medial buttress" or swelling on the inside of the joint to develop. This is usually a sign that arthritis has already started in the joint. Radiographs (x-rays) are not always helpful in diagnosis, but they are usually recommended to rule out any other issues or to assess if arthritis has started to develop. But radiographs are required for certain types of surgical repairs. Here is a link to a picture of a ruptured cruciate.
Rascal has to have surgery? You are very worried about putting him under anesthesia. Can't he just rest and take some anti-inflammatory medication? Unfortunately, the only treatment for an ACL rupture is surgery. If it is not surgically repaired, osteoarthritis will start developing in the joint (sometimes in a matter of weeks), leading to chronic pain and decreased mobility. Yes, not doing surgery IS an option, but it is NOT a very good option especially with large dogs. To be blunt, not doing surgery essentially dooms your dog to a lifetime of pain and lameness. I know that is a little harsh, but I'm trying to be honest with you all. And yes, we are fully aware that oftentimes an owner's finances just simply don't allow for surgery, but if you have to scrimp and save to get your dog surgery - DO IT. Please. People don't always require surgery when they tear an ACL, but this is because of the different biomechanics of canine versus human legs. Dogs are different than people.
There are three types of surgical repairs commonly performed - an extracapsular or lateral suture repair, a tibial plateau leveling osteotomy (TPLO) or a tibial tuberosity advancement (TTA). I'm not going to go into a description of the three surgeries here, because frankly, all the talk of biomechanics and confirmation would likely bore the average reader to tears. And if your dog does rupture their ACL, you'll be talking to your veterinarian about your options anyway. The decision to perform one surgery versus another will depend on a variety of factors including your dog's size, weight and confirmation as well as surgeon preference. Finances do also often play a role since the extracapsular repair is generally less expensive. The TPLO and TTA procedures are preferred for large breed dogs, but you may need to go to an orthopedic specialist for these surgeries.
Dogs will typically stay in the hospital at least overnight after surgery. Most go home the next day, getting around remarkably well on three legs. Some dogs will even bear a little weight on the leg if a TPLO or TTA was performed. These two surgeries are reported to have a quicker return to function than the extracapsular repair. Antibiotics and pain medication is standard. Dogs are not usually sent home with a bandage, but an e-collar (or "cone of shame") may be necessary to prevent licking at the incision. The main part of recovery is STRICT REST for at least two weeks, followed by roughly six weeks of slowly increased activity and physical therapy. And STRICT REST means NO running, NO jumping, NO stairs and only short leash walks outside to urinate/defecate. This is the hardest part for most owners. Your dog has to stay quiet to allow the surgery site to heal properly. Things can go wrong. Implants can fail. Bone can fail to heal and fuse. Dogs are NOT smart enough to restrict their own activity. The quieter they stay, the quicker they will heal and get back to chasing squirrels. Usually at the time of suture removal (10-14 days after surgery), your veterinarian will give the go-ahead to start slowly increasing activity and start physical therapy. By roughly eight weeks, your dog should be approaching normal activity and use of the leg. Physical therapy is also beneficial for many dogs following surgery, whether it is simple passive motion or an underwater treadmill.
And then Rascal will be fine after surgery? Well, it depends. With minimal to no arthritis in the joint, most dogs do just great following surgery and can return to a normal activity level. If the rupture was more chronic in nature, more significant arthritis is usually present and dogs will never be 100% in the affected leg. The other really important thing to remember is that many dogs often rupture the other ACL within a year or two. Yes, you might be going through the whole ordeal all over again. Bummer, isn't it?
We average roughly one ACL repair per week. This is one of the most common orthopedic injuries we see and we see it a lot. Unfortunately, there really is not a whole lot you can do to prevent your dog from tearing their ACL. If it's going to happen, it's going to happen no matter what you do. However, keeping your dog at an ideal weight has a huge impact on speed and ease of recovery. If Rascal is a little "chunky monkey", he's going to have a harder time getting around on three legs after surgery, right? (An obese dog is also harder on your back when you have to help your dog get around following surgery!) Obesity obviously puts a greater strain on joints and will exacerbate any arthritis. A lean, fit dog will bounce back much faster from surgery than an obese dog. Luckily, Rascal is fit and trim. You decide to go forward with surgery and by mid-summer, he is back in the park....chasing more squirrels.
Special thanks to Hills for their Atlas of Veterinary Clinical Anatomy for providing the anatomical pictures.