There are two bands of fibrous tissue called the cruciate ligaments in each knee joint. They join the femur and tibia (the bones above and below the knee joint) together so that the knee works as a hinged joint. They are called cruciate ligaments because they “cross over” inside the knee joint. One ligament connects from inside to outside the knee joint and the other outside to inside, crossing each other in the middle.
Humans have the same anatomical structure of the knee. Cruciate ligament rupture is a common knee injury of athletes. Rupture of the cranial cruciate ligament of the knee joint is the most common orthopaedic injury in dogs especially in Rottweilers. It results in hind leg lameness which may appear suddenly or progress slowly over weeks to months.
The knee joint (or stifle) has a number of important parts. The function of the Cranial Cruciate Ligament (CCL) prevents the tibia from pushing forward and rotating inward and provides general stability to the knee joint.
Rupture of the Cranial Cruciate Ligament
Injury may occur after such actions as: sudden starts, sudden stops, tight turns, jumping and running. Pretty much all the fun things dogs enjoy doing! Cruciate tears may occur suddenly (acute) or more chronically over time. Most owners notice a limp, stiffness, pain and sometimes, swelling or heat in the joint. In some dogs, the cause of CCL rupture is unknown. It often appears to involve premature degeneration of the ligament and/or abnormal alignment of the knee bones. Occasionally a traumatic event or vigorous exercise precedes rupture but many dogs “seem fine one minute and lame the next”. Whatever the cause, rupture results in instability, pain, lameness, joint swelling and eventually arthritis.
How is it diagnosed?
With traumatic cruciate rupture, the usual history is that the dog was running and suddenly stopped or cried out and was then unable to bear weight on the affected leg. Many pets will “toe touch” and place only a small amount of weight on the injured leg. During the examination, the veterinarian will try to demonstrate a particular movement, called a drawer sign. This indicates laxity in the knee joint. Many dogs will require sedation or anaesthesia before this test can be performed due to the severe pain they are experiencing. Other diagnostic tests such as radiographs (x-rays) may also be necessary. Tests such as arthroscopy may be needed to rule out other damage to the joint. Diagnosis is made by examination of the knee joint and identifying instability. Sometimes sedation or anaesthesia is required to make a definitive diagnosis. Occasionally, findings on X-Rays are utilized to support suspicion of CCL rupture and to rule-out other causes of hind leg lameness.
Is obesity such a problem?
Obesity can result in cruciate ligament rupture. If your dog is overweight, the recovery time will be much longer. Obesity also increases the risk of injury to the other knee. Weight loss is as important as surgery in ensuring rapid return to normal function.
Initial treatment is usually rest and anti-inflammatory medications. Most smaller dogs, those weighing less than 10 kg, do very well with rest and anti-inflammatory medication. However, most dogs weighing greater than 10 kg (and some less than 10 kg) require surgery to have a satisfactory outcome. As a general rule, if a pet remains lame, or again becomes lame, after 2-4 weeks of initial treatment, surgery will eventually be necessary. At some point, surgical intervention is required to restabilize the joint; however not all pets are candidates for surgery. There are several different techniques to restabilize the joint and your veterinarian will guide you as to which procedure is right for your pet.
Physical rehabilitation is used both pre and post operatively to treat joint pain and swelling, promote better joint range of motion, improve weight bearing and thigh muscle mass. This can be done using a variety of modalities including manual therapy, aquatic therapy, low level laser, exercise and thermotherapy.
Cruciate or canine knee braces play a pivotal role in being able to maintain stifle stability, while maintaining adequate weight bearing in the limb to limit thigh muscle atrophy. The vets will custom make a brace for your pet to support the stifle in an anatomically correct position. This will allow your pet to walk, bear weight and limit the stress and strain on the other limb.
These braces are also extremely useful after surgery. They allow for weight bearing and support as tissue heal and take the load off the other knee. They can also be used during the rehabilitation process.
Surgical Repair of Cranial Cruciate Ligament Rupture Important Facts:
♦ Most dogs weighing more than 10 kg (and some less than 10 kg) need surgery for satisfactory outcome.
♦ A successful outcome with surgery is expected in 90-95% of cases.
♦ Regardless of the treatment, some arthritis will develop in the knee.
♦ General anaesthesia is utilized for the procedure
♦ The faint scar remaining after surgery usually becomes covered with fur again.
♦ An overnight stay is required so discomfort can be controlled with injectable pain medication.
Goals of Surgery:
♦ Relieve pain associated with the ligament injury.
♦ Stabilize the knee joint in a more anatomically correct position
♦ Decrease the amount of arthritis which will inevitably develop in the knee.
♦ Limit stress put on the opposite limb and other limbs and joints.
♦ Many different procedures exist for the stabilization of the knee joint.
♦ No procedure has been shown to be superior to the others over the long term.
♦ The ligament itself is typically too damaged to be repaired or replaced
Repair of the injured knee involves three important steps
1. Exploration of the joint to confirm the diagnosis and identify the extent of damage.
2. Removal of damaged ligament and cartilage.
3. Stabilization of the knee joint with a thick nylon suture or artificial ligament. The suture is placed around the fabella and through the tibia.
♦ The recuperative period typically lasts for a total of 8-12 weeks.
♦ Pets gradually begin to put weight on the operated leg over the first 14 days.
♦ Physical therapy comes in the form of progressively longer leash walks over the following weeks.
♦ Initially, exercise is limited to walks to eliminate only.
♦ Skin sutures are removed 10-14 days after surgery.
♦ Exercise on leash is gradually increased over the following weeks; swimming is also excellent exercise.
♦ Pain medication and antibiotics are administered for several days after surgery.
♦ No running, jumping or playing is permitted for at least 12 weeks following surgery.
Outcomes, Complications, and Risks:
♦ Most pets are permitted to resume normal activity several months after surgery.
♦ As many as 30% of dogs will require surgery on the opposite knee in the future.
♦ 5-10% of dogs have lameness after surgery which is controlled with medication.
♦ Rarely the artificial ligament needs to be removed or replaced. Infection after surgery makes additional surgery (or even amputation) necessary.