Cranial Cruciate Ligament Rupture
By Roger Ross DVM
One of the more common lameness injuries we see in dogs is caused by the tearing or damage of the cruciate ligament in the knee.
Dog and cat knees are similar to humans knees. Damage to the cruciate ligament is also a common injury in humans...especially athletes. Sometimes it doesn't take much; just a misstep or a twist when landing from a jump. Any of the structures in the knee can be damaged, but in both humans and dogs, the most common injury is to the anterior or cranial cruciate ligament. Damage to this ligament leads to an unstable knee and it hurts. Especially for the first few weeks after tearing the ligament.
By the way, the ligament is similar to twine in that it's made up of many twisted fibers. When just some of the fibers are torn we usually describe the injury as a ligamental tear. When the entire ligament is torn, we say it is ruptured. Actually, such nomenclature is sort of meaningless in the sense that it's hard to tell on physical exam how badly damaged the ligament is, because either way it hurts and on exam there's excessive play in the joint.
It does matter, though, in terms of healing. Without surgery, a completely torn ligament has no chance of healing. But with a little luck, time, and support, a partially torn ligament might heal without surgery. Especially if the patient is small and not too active.
If you have a limping pet, your vet has a good chance of detecting the cause during the initial exam because she or he will be able to detect the excessive play in the joint.
However: sometimes the veterinarian who first examines your pet misses the problem because the initial swelling and inflammation from the injury hides the excessive joint play, so understand that the cruciate damage may not be detected at first. If you didn't know this, you might think the first vet was stupid. But if you think about it, there's a lot of situations in life where it's necessary to check your work a second time before you discover what you're looking for.
The cruciate ligament keeps the femur (upper leg bone) from sliding too much on the tibia (lower leg or shin bone) when you put weight down. Without a healthy, intact cruciate ligament, this extra sliding causes wear and tear on the joint cartilage (and miniscus).
This really hurts at first, but given time and rest the initial pain resides and a lot of pets will start using their injured limb again after a month or so. But because the knee is less stable, re-injury is much more likely. And if the knee isn't repaired surgically, it's very likely that the knee will become arthritic with time.
What To Expect When You Go To The Vet
(Of course, other vets may do things differently)
A Good Exam and History.
If your pet is limping, we will check out the entire pet to assess general health and other problems. We will want to know how long your pet has been limping and if there have been other rear end problems in this patient. We will check out the toes and paws, check for abscesses, feel the lymph nodes behind the knees and in the inguinal or crotch region. We will stretch out the leg, and do a series of range of motion tests...all of which will narrow the problem down to the knee if your pet's problem is a torn cruciate ligament. There are a couple of simple motion tests we will do looking for excessive play in the knee called "drawer movement" which is tell tale for curciate tears. This is often simply and quickly determined by an experienced vet, but sometimes it will take a little extra effort (see below) to pin the problem down. And as I mentioned in the introduction, sometimes we miss the problem entirely during the first visit, but pick it up in the recheck visit.
Also, lack of drawer movement doesn't rule out cruciate tears: partial tears that don't result in drawer movement are common and can be quite difficult to diagnois.
Another sign your vet will be checking for is scar tissue to thickening called a buttress on the medial or inside side of the knee. This scar or bony reactive tissue isn't present early on in the disease but is noticed after several months of stress to the joint.
Once your vet detects excessive drawer movement suggesting a torn cruciate ligament, he or she may want to:
1. Run blood work to see if there is a high white blood count indicating infection of the joint, electrolyte or mineral imbalances, and as a routine check of other organs prior to anticipated anesthesia and surgery
2. Sedate or pet to allow better range of motion tests and palpation of the joints and limb. Sometimes pets are too antsy, tense, or resistant to do a good lameness exam without muscle relaxers or sedation.
3. Your vet may trot your pet and then recheck the limb. Sometimes the lameness is more evident after a little workout.
4. Radiograph the knee to rule out damaged bone and cartilage structures. And while ligaments don't show up on xrays, they are still quite useful: radiographic evidence of increased joint fluid is usually associated with cruciate tears.
5. Fancier Stuff: Other vets may have more sophisticated equipment and experience and may suggest an MRI or scoping the joint.
Conservative, Non-Surgical Treatments:
1. Short term steroids, other anti-inflammatories, and pain medication for the intial swelling and pain are likely to be used at first whether or not you elect to surgically repair the knee in the future.
2. Forced Rest and/or support bandages are often helpful in getting the swelling and inflammation under control quickly. This also prevents further damage to the joint.
3. Heat wraps, Heat Rubs, BenGay etc.
NOT Recommended I mention this possible treatment because a lot of people are used to using this type of treatment on themselves and on horses with lamenesses.
But we rarely use heat rubs on dogs mainly because they get sick when they lick them off. I suppose heat wraps might have some benefit, but I haven't heard of any vet using them. It's difficult to wrap dog knees.
4. Glucosamine, MSM, Anti-Oxidants, and Omega 3 Fatty Acids might very well be recommended for their properties of reducing damage and speeding healing of cartilage etc. I like and trust the Glycoflex supplements you can get directly from the company on line (VetriScience) If you go to their website the user name = fox the pass word = pets75
5. Pain management. I like using Duralactin and Rimadyl but there is a wide choice of appropriate pain medications your vet might choose.
6. Weight loss. Being fat puts a lot of extra stress on joints.
7. Time, rest, and patience. Most patients with cruciate damage would benefit from surgery. But, if for reasons of money or other circumstances you elect to avoid surgical repair, your pet will probably heal without surgery to the point where it will use the leg ginergly or adequately. It all depends, but the more active and robust and big the dog, the more likely your pet will have life time problems and pain using the leg unless the problem is corrected surgically. Surgery will also minimize future arthritis.
There are quite a few different types of surgical repair techniques done on damaged cruciates in both humans and pets. That's because no one has come up with a perfect repair procedure yet. Whenever we in medicine discover a great treatment procedure for a problem, it doesn't take long for word to get out and soon that's the way everybody does it, because it's the best. But there are lots of problems for which we have helpful treatments or surgeries but not perfect solutions...fixing damaged knees are in this latter category.
But nothing is more likely to make your pet weight bearing and functional again than surgery. Nothing is as likely to minimize and prevent future arthritis, pain, and further injury than surgery.
The most common types of knee surgery involves connecting the back of the femur to the front of the tibia using heavy suture material or surgical wire. This tightens up the joint and reduces slipping and sliding. Over time, scar tissue will cover the suture and act somewhat like the original ligament.
Most pets recover full or near normal use of the knee over a period of 1-3 months.
Post Op Monitoring
It's important to rest the knee after surgery and to daily check the support bandaging for slippage, abrasions, ulcers, and odor. Your pet will probably be on post op medications for pain and inflammation. I often prescibe short term sedatives if needed for "over active" pets.