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 after middle age. 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.
In the picture to your left, you can appreciate how small and fragile this ligament is compared to the heavy ligaments on the side of the knee and over the knee cap. This little piece of fibrous tissue is what keeps the the two bones from sliping and sliding against each other.
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 or injury.
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 knee and it hurts.
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: we sometimes can’t tell why your pet’s knee area is tender and swollen on initial exam. Is it just a sprain: A fracture? A meniscus tear? A cruciate tear? Just a bruise?
But because the knee is swollen, it’s difficult to flex and extend… or to check for excessive play.
So, we sometimes just treat the swelling and inflammation at first and if the dog isn’t much improved in 1-2 weeks, we recheck. And because the swelling has gone, we can then detect the excessive slip and slide known as “drawer movement”
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 meniscus).
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 and flare ups of lameness and discomfort are likely.
And if the knee isn't repaired surgically, it's very likely that the knee will become arthritic with time.
So… if your pet ends up with and injured cruciate ligament…
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 the diagnosis, on palpation is quite uncertain.
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 weeks-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. Sophisicated Diagnostics: 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 lameness’.
4. Laser Therapy. I’m impressed at how often and how well this helps to reduce swelling, inflammation, and pain. And the energy delivered deep into the tissue stimulates cell metabolism which speeds healing significantly.
5. 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.
6. Pain management. I like using Duralactin. Tramadol, and Rimadyl but there is a wide choice of appropriate pain medications your vet might choose.
7. Weight loss. Being fat puts a lot of extra stress on joints.
8. 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 gingergly or adequately.
It all depends, but the more active, robust, and heavier 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.
9. Stem Cell Therapy. This very newly available option (2013 I believe) is apparently working extremely well on many types of joint diseases. At present the $3000-8000 treatment cost is too prohibitive for most practices to consider.
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 someone discovers a great treatment or procedure for fixing a medical problem, it doesn't take long for word to get out and soon that's the way most everybody does it, because it's the best.
But there are lots of problems for which we have treatments or procedures that help a lot, but not 100% … fixing damaged knees are in this category.
But nothing is more likely to make your pet weight bearing and functional again than surgery.
And nothing is as likely to minimize and prevent future arthritis, pain, and further injury than surgery.
There are several different surgical techniques commonly used to make the knee stable again.
Explaining the advantages and disadvantages of the different techniques is above my pay grade. But your vet or the veterinary orthopedic specialist that you are referred to will gladly go over this with you.
Most pets recover full or near normal use of the knee over a period of 1-3 months.
Post Op Monitoring
Rest, rehab, and recheck will be needed.