Cranial Cruciate Ligament (CCL) Injury
The most common canine condition seen at VOSM is a cranial cruciate ligament (CCL) injury. The cranial cruciate ligament is commonly equated to the ACL in humans.
As frequently recommended in humans, surgical intervention is typically needed to return your dog back to normal activity. There are multiple procedures that are available to treat this injury and at VOSM we make specific recommendations that are tailored to the individual.
To date, there is no "best" CCL procedure. However, we believe there is a "best" procedure for each individual dog. VOSM's surgeons have performed thousands of CCL repairs, including the tibial plateau leveling osteotomy (TPLO), TightRope (TR), tibial tuberosity advancement (TTA), and lateral suture/extracapsular stabilization. We base our recommendations for stabilization on the following criteria.
- Activity Level (companion pet vs. performance or working dog)
- Medical History
- Stifle (knee) anatomy (tibial plateau angle/slope)
The VOSM Approach
At VOSM, we specialize in a minimally invasive approach to the knee joint including arthroscopic techniques or use of a mini-arthotomy using a keyhole incision into the stifle (knee).
We do not perform full arthrotomies (complete opening of the knee joint) due to the increase in pain, inflammation, and prolonged recovery.
At the time of surgery, the condition of the meniscus (the shock absorber in the joint) is evaluated. Damage to the meniscus can lead to prolonged pain and lameness as well as the progression of osteoarthritis. It is imperative that the meniscus be thoroughly evaluated and treated appropriately at the time of surgery.
Recovery & The Role of Physical Rehabilitation
Following knee stabilization, dogs typically return to normal function within 12 weeks with proper physical rehabilitation. We evaluate at 4, 8, and 12 weeks to ensure your dog is progressing well. Both bone healing and muscle mass are evaluated closely by our rehabilitation therapists as unresolved muscle weakness may lead to additional compensatory conditions/injuries.
Similar to humans having ACL surgery, physical therapy is an integral part of the recovery for our canine patients. Rehabilitation therapy following CCL surgery includes range of motion, stretching, muscle-building activities, massage, therapeutic ultrasound, cold laser, TENS, hydrotherapy, and a home therapeutic exercise program.
During each rehab session, patients are reassessed and a tailored program is designed.
It is reported that once a dog injures one knee, it has a 50% or greater chance of injuring the other knee. This may be due to excessive weight bearing on the "good knee" following injury. Therefore, we believe that early surgical treatment and rehabilitation therapy are imperative to help protect the other knee.
Regenerative medicine may be considered for patients with very early partial tears. The knee is evaluated arthroscopically and if a small percentage of breakdown is noted (less than 50%), this treatment may be considered.
For canine patients that are not surgical candidates due to age, medical conditions or other concerns, a functional hinged knee brace may be considered. A casting of the knee is created by our therapists, which is then shipped to an orthotist for creation of the custom device. This process typically takes 14 days. Once returned, the canine patient is fitted at VOSM and home instructions are demonstrated by the therapist or technologist.
What is a CCL and what does it do?
Although the knee (stifle) joint in dogs is similar to ours, the forces applied to the joint doing weight bearing are vastly different.
Our hip, knee and ankle joints are perpendicular to our weight bearing surfaces: our feet. When we stand, there is minimal stress to the ligaments in our knees. Dogs, however, stand on their toes with the ankle elevated and the knee forward. The top of the dog's tibia (tibial plateau) is sloped and weight bearing creates a force that pushes the femur down the slope of the tibia. This force is called "tibial thrust," and it is the job of the CCL to prevent this motion.
Each time the dog bears weight, the CCL is called to work. If you think of the tibial plateau as a hill and the femur as a car parked on that hill, the CCL is the parking brake. If the ligament ruptures, it allows the femur to slide down the slide or, in our example, the brake releases and the car rolls down the hill.
When the ligament is ruptured, each time the dog bears weight this motion occurs and causes discomfort. Within the joint, there may be inflammation and swelling, referred to as synovitis and effusion.
The menisci are the "shock absorbers" of the knee and are located between the bottom of the femur and top of the tibia. There is a meniscus located on the inside (medial) and outside (lateral) aspects of the knee. When the knee is unstable due to a CCL rupture, either complete or partial, these structures are at risk for injury.
How does a rupture of the CCL occur?
Rupture of the CCL can occur in several ways.
A single incident may cause sudden, complete rupture of the ligament. When this occurs, the dog is typically painful and non-weight bearing. The rupture can also occur over time. Dogs with a high tibial plateau angle (greater slope) have greater stress to the CCL and the ligament can tear incrementally. Dogs can also partially tear the ligament due to an incident.
With a partial rupture, the dog typically experiences an intermittent lameness. The majority of partial ruptures will progress to complete ruptures within weeks or months.
Common causes of partial and/or complete ruptures include hyperextension and internal rotation of the knee from sudden turns, stepping into a hole, jumping (if the force of the cranial tibial thrust exceeds the breaking strength of the CCL), repetitive normal activities, and degeneration with aging.
Obesity can increase the risk of a rupture, as can the "weekend warrior" routine, in which the pet is relatively inactive during the week but very active on the weekend.
Dogs that have ruptured the CCL in one knee have a 50-70 percent greater chance of rupturing the other CCL. Therefore, surgical correction is recommended as soon as possible to decrease the stress placed on the uninjured CCL, thereby decreasing the risk of CCL rupture to that knee.
What are signs that my pet has a CCL rupture?
If the CCL rupture is complete and acute, often the pet will be non-weight bearing lame. With rest, the lameness may improve but will return as the pet is more active. However, in the case of a partial or gradual rupture, the pet will be weight-bearing lame or have intermittent lameness. Lameness will often worsen with activity. Stiffness upon rising and/or a stiff gait are other common complaints.
You may not that your pet sits with the affected leg out to the side. He or she may have trouble rising or be less active. Physically, you may note swelling or thickening of the knee and muscle atrophy in the affected limb. Dogs with two ruptured CCLs often do not off-load or carry either limb, as neither is particularly comfortable to stand on.
How is a CCL rupture diagnosed?
Diagnosis of a CCL rupture requires an orthopedic examination. This exam often begins with a visual analysis. Lameness at a walk and off-loading when standing are often observed. Lameness may be mild to non-weight bearing. The patient will often demonstrate a positive "sit test," in which the affected limb is out to the side rather than tucked against the body.
The musculature of the hind limbs will be assessed. Muscle atrophy of the affected hind limb is common. Often, especially in chronic cases, thickening of the affected knee, called medial buttress, is noted. The patellar tendon, which runs along the front of the knee, is assessed. The edges of the patellar tendon are easily palpable in a healthy knee, but effusion within the joint, common with CCL injuries, will make palpation of the patellar tendon less distinct.
Joint stability can be assessed through manual manipulation. The "cranial drawer" test involves holding the femur with one hand and the tibia with the other, testing for forward motion of the tibia in relation to the femur, called cranial drawer or cranial thrust. This forward tibial drawer or thrust is tested throughout range of motion of the knee. Motion elicited only in flexion typically indicates a partial rupture of the CCL. Motion elicited throughout range of motion often suggests a more complete rupture. A nervous patient with good quadriceps muscle tone can make this test challenging.
Cranial thrust can also be evaluated by applying tibial compression. This technique involves placing the index finger of one hand over the patella (kneecap) with the tip resting on the tibial crest and flexing of the hock (ankle) with the other hand. An intact CCL will prevent forward motion of the tibia during hock flexion; therefore, if tibial thrust is elicited, the CCL is likely compromised.
Radiographs of the stifle can be useful in evaluating the presence of effusion (excessive fluid within the joint) and arthritis. If these assessments are not completely diagnostic, arthroscopic evaluation of the joint and structures may be recommended. If arthroscopic evaluation reveals the ligament is injured, surgical correction can be performed at that time.
What surgical options exist for CCL repair?
Traditionally, there are four surgical options: the tibial plateau leveling osteotomy (TPLO), TightRope, tibial tuberosity advancement and extracapsular stabilization (lateral suture).