Rupture of the cranial cruciate ligament (CCL) is a common problem in dogs. The cranial cruciate ligament in dogs is comparable to the anterior cruciate ligament (ACL) that is commonly injured in human athletes. Injury to this ligament in people is typically associated with some type of extreme trauma. In dogs, however, the ligament most typically ruptures during normal activities without any abnormal stress on the knee.
The knee is located on the back leg between the femur and the tibia. There are four ligaments present in the knee of dogs. These include the cranial and caudal cruciate ligaments and the medial and lateral collateral ligaments. (figure 1) Each ligament has a different function in stabilizing the knee joint of dogs. Ligaments are strong tissues that connect two bones. The cranial cruciate ligament is by far the most commonly damaged of all the knee structures. It is composed of two separate bands that function differently at various knee angles. Approximately 25 to 30% of dogs with cruciate ruptures will have tearing of only one band, which is referred to as a partial cruciate rupture. Most dogs however will have a complete tear involving the entire ligament.
The canine cranial cruciate ligament is thought to rupture because of continual stresses placed on the ligament during walking and running. This continual stress is primarily a result of the shape of the top of the tibia. The caudal or back portion of the top of the tibia is angled or sloped down hill. This is referred to as the caudal tibial slope. (figure 2) During weight bearing movement, the femur pushes into the caudal tibial slope. The pressure between the femur and tibia at this location causes the tibia to shift forward, producing repeated stress on the cranial cruciate ligament when weight is placed on the limb. This is believed to play a major role in rupture of the ligament in dogs.
Two other important structures in the dog knee are the medial and lateral menisci. These are C- shaped pieces of cartilage located inside the joint between the femur and tibia that help to stabilize the knee. (figure 3) The medial meniscus is commonly damaged in association with rupture of the cranial cruciate ligament. Meniscal tearing is painful and if a torn meniscus is identified at surgery it will be at least partially removed.
What animals are most commonly affected?
Medium to large breed dogs (e.g. retriever breed size) between the ages of 6 and 10 years are most frequently affected. However, dogs as young as 1 to 2 years old and of any size including toy and giant breeds can rupture their cranial cruciate ligament. Cats also will occasional develop limping because of a ruptured cranial cruciate ligament.
What are the common signs of a cranial cruciate ligament rupture?
Dogs will typically develop a sudden onset of non-weight bearing lameness. This will usually improve over a few weeks. Occasionally, an animal’s owner will identify an abnormal incident that caused the lameness such as falling off a deck or stepping in a hole. Most often however no incident is identified and animals become lame while performing every day activities such as running and playing.
How is a cranial cruciate ligament rupture diagnosed?
Nearly all dogs with tearing or damage to their cruciate ligament will have swelling that is felt on the front part of their knee. Your veterinarian will most likely be able to feel this swelling. A definitive diagnosis of a complete cranial cruciate ligament rupture is based on palpable laxity or looseness of the affected knee. This laxity can be felt without sedation in some dogs but others will need to be sedated in order to identify the instability. This looseness is called cranial drawer instability. The diagnosis of a partial cruciate ligament rupture is more difficult. Dogs with partial ligament tears will usually have swelling of their knee and pain when their knee is completely extended. A definitive diagnosis however is inevitably made during exploratory surgery of the knee.
Dogs with longstanding complete or partial cruciate tears will commonly develop thickening on the inside of their knee, which is known as a medial buttress. They will also have arthritis visible on radiographs taken by your veterinarian. Radiographs are taken to make sure no other problems exist in the knee such as infection or cancer and to show how much arthritis is present. Occasionally, fluid will need to be collected from the joint if any question exists about the possibility of a joint infection, cancer or other knee conditions.
Are there any other possible causes of my pet’s limping?
Yes, but other causes are very uncommon. Generally the diagnosis is extremely straightforward. Other possible causes of rear leg limping include joint cancer, joint infection, trauma and auto-immune diseases. Some indication of one of these diseases will almost always be seen on a complete physical examination or radiographs of the affected knee. If anything about your dog’s limping does not “add up”, other tests such as blood work or joint fluid analysis will be recommended. This is fortunately not necessary in most dogs.
Will my dog rupture the cruciate ligament on his/her other leg?
Approximately 40 to 50 % of dogs with one cranial cruciate ligament rupture will rupture the ligament on the other rear leg within two years of the first rupture.
What are my treatment options?
The recommended treatment for a cranial cruciate ligament rupture is based on the size of your dog. In general, dogs that are less than 30 pounds do not require surgery. Instead, medical management is appropriately recommended. Medical management involves strict confinement for 6 to 8 weeks and administration of non-steroidal anti-inflammatory medications (NSAIDs). If this does not result in acceptable improvement, then surgery should be considered.
Surgery is recommended for dogs that weigh more than 30 pounds. Several surgical options exist. Most surgical procedures attempt to recreate the function of the cranial cruciate ligament in some way. The most commonly performed procedure is called a lateral fabello-tibial suture stabilization. This surgery uses a heavy sterile suture material to stabilize the knee. The suture runs in the same direction as the cranial cruciate ligament and therefore provides the same approximate function as the ligament.
More recently tibial plateau leveling osteotomies (TPLO) are being performed to treat cranial cruciate ligament ruptures in dogs. This procedure is most commonly performed in dogs weighing greater than 50 pounds but can be performed in dogs as small as 10 pounds. The TPLO does not replace the ruptured cranial cruciate ligament. Instead it changes the forces that act on the knee and eliminates the need for the ligament. The surgery involves a circular bone cut in the tibia just below the knee (Figure 4). This bone cut allows rotation of the top of the tibia, which in turn stabilizes the knee. After the bone is cut it is held in place with a bone plate and screws. (figure 4)
Are there any potential complications associated with surgery?
With any surgical procedure there is the potential for complications. Potential complications associated with any cruciate surgical procedure include problems with general anesthesia, incisional infection (3 to 4% of surgical sites), implant breakage, and failure to improve function (less than 10% of animals). More than 90% of dogs benefit from both the lateral fabellotibial suture and the TPLO surgeries. We feel that a better outcome occurs more predictably with the TPLO procedure than with the lateral fabellotibial suture stabilization. Finally, less than 10% of dogs will have a significant complication.
How will I take care of my dog following surgery?
Activity restriction: Your dog will need to have its activity controlled for 8 to 12 weeks following surgery. For the entire 8 to 12 weeks of recovery, your dog should avoid slippery surfaces (e.g. slick concrete, hardwood floors, tile, etc.) and long flights of stairs. He or she should be confined to a single room without access to jump on furniture when not on a leash. Your pet should not be allowed to play with other animals or people and should be on a short (i.e. less than 6 foot) leash and under your complete control at all times when outside.
Two situations pose a potential problem following surgery. One is continuous walking on the operated limb. This repeated stress increases the chances of a complication associated with healing of the incision and the deeper tissues (i.e. joint and bone) and predisposes the implants (i.e. bone plate and screws) to fail. The other is a sudden burst of energy causing extreme stress on the surgical site. This is the worst of all possible scenarios. It is therefore essential that your dog is on a leash under your complete control at all times while outside during the 8 to 12 weeks following surgery. If your dog has had a TPLO procedure he or she will only be able to return to normal activity after radiographs have confirmed bone healing. Healing is almost always complete by the end of 12 weeks.
Care of the incision: During the first 2 weeks after surgery, special attention needs to be paid to the surgical incision. You should watch for any type of cloudy or foul smelling drainage, opening of the incision, or excessive swelling. Swelling associated with the incision should progressively decrease over 2 weeks. To minimize swelling, the incision can be cold packed for 24 hours following returning home. The incision should then be hot packed 3 to 4 times daily for 5 more days. If your dog has any tendency to lick or chew its incision, then a protective Elizabethan (i.e. lampshade) collar will need to be purchased and worn by your dog at all times until the time of suture removal.
Recheck examinations: Recheck examinations are generally scheduled for 2 weeks following surgery for suture removal and 8-10 weeks for final examination. If your dog has had a TPLO, he or she will have radiographs taken at the final recheck visit.
Medications: Your veterinarian will provide you with instructions about medications to be taken following surgery. Generally some type of pain medication will be administered for 5 to 7 days following surgery.
Should I do physical therapy on my dog following surgery?
For dogs operated with a lateral fabellotibial suture, we recommend physical therapy in the post-operative period starting 4 to 5 days after surgery. The most simple form of physical therapy involves moving the operated knee through a full range of motion repeatedly for 10 to 15 minute sessions 3 to 4 times each day. This should continue for approximately 4 to 6 weeks following surgery. If you have any other questions about physical therapy consult your veterinarian.
- Cranial cruciate ligament rupture in dogs is similar to anterior cruciate ligament rupture in people.
- Approximately 30% of dogs with cruciate ruptures will have partial tears of the cranial cruciate ligaments.
- Approximately 50% of the dogs with cruciate ruptures will tear the cranial cruciate ligament on their other leg within 2 years of the first tear.
- Dogs with CCLR most often go to the veterinarian because of a sudden onset of non-weight bearing on a rear limb.
- Most of the time an animal owner will not see a reason for the sudden lameness.
- A definitive diagnosis is made when your veterinarian feels abnormal looseness in the affected knee.
- Surgery is recommended for all dogs weighing more than 30 pounds
- The two most common surgeries are tibial plateau leveling osteotomy and lateral fabellotibial suture.
- Greater than 90% of dogs improve with surgery.
- Potential surgical complications include:
- problems with anesthesia
- infection of the incision
- implant breakage
- failure to improve
- Activity restriction is required for 8-12 weeks following surgery.