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CRANIAL CRUCIATE LIGAMENT RUPTURE
Overview
Cranial (or anterior) cruciate ligament (CCL) rupture is one of the most common orthopedic conditions seen in the dog. (Figure 1)
Figure 1. Arthroscopic view of a partial cranial Cruciate ligament tear.
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Unlike in people, where trauma is the most common etiology of the disease, canine CCL rupture is multifactorial in origin. Regardless of cause, CCL rupture results in stifle instability which sets into motion a cascade of events including synovitis, articular cartilage degeneration, periarticular osteophyte development, capsular fibrosis and medial meniscus injury. (Figure 2) Progressive osteoarthritis is the end result after cranial cruciate ligament rupture regardless of treatment; however, the severity of osteoarthritis may be attenuated with early surgical intervention.
Figure 2. Open arthrotomy with osteoarthritis
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Causes
CCL rupture may be acute or chronic in nature. Acute injury to the CCL is usually traumatic in origin and is a reflection of its function as a stabilizer of joint motion. Acute injury is most commonly associated with hyperextension and internal rotation of the leg which occurs when the dog steps in a hole or becomes ensnared in a fence. Jumping can also cause cruciate ligament rupture if the forces stressing the ligament exceed its breaking strength. Proposed underlying etiologies for chronic disease include age related deterioration to the ligament structure, obesity, conformation abnormalities (straight rear limb conformation), and immune mediated disease. With ligament degeneration, even repetitive normal activities can cause progressive rupturing of the ligament.
Incidence and Prevalence
Either sex and any age or breed of dog may be affected. CCL injury is rare in cats. Recent epidemiological studies have suggested that younger, more active large breeds of dogs may be predisposed to CCL rupture.
Signs and Symptoms
Depending upon the nature of the injury (acute or chronic) and whether the rupture is complete or partial, the clinical presentation can vary from a subtle lameness associated with exercise to a full non-weight bearing injury. Patients with acute tears usually present with a non-weight bearing or partial-weight bearing lameness of sudden onset. This lameness usually improves within 3 to 6 weeks after injury without treatment, particularly in patients weighing less than 10 kg (25 lb). Retrospective studies of dogs weighing less than 10 kg indicate that they typically have adequate clinical function with conservative treatment. In mid-size and large breed dogs, the lameness associated with CCL injury improves but the animal never returns to full athletic function without evidence of recurring lameness. Furthermore, a knee deficient of a CCL predisposes the animal to injury to other structures within the knee, such as the menisci, which are the shock absorbers of the knee. Damage to the menisci results in progression of the osteoarthritis and lameness. Partial cranial cruciate ligament tears are difficult to diagnose in the early stages of injury. Initially, affected animals have a mild weight-bearing lameness associated with exercise, and until degenerative changes develop, the lameness resolves with rest. Later, however, as the ligament continues to tear and the stifle becomes increasingly unstable, degenerative changes worsen and lameness becomes more pronounced and does not resolve with rest.
Risk Factors
Risk factors include large, active dogs (such as Rottweilers, Labradors and Golden retrievers), obesity, and animals that participate in the weekend warrior syndrome (intermittent excessive activity by inactive dogs and their owners).
When To Seek Veterinary Surgical Advice
Any time an animal displays lameness or pain greater than one week that is non responsive to conservative treatment of rest and anti inflammatories drugs, the animal should be examined by a veterinarian. If surgery is advised, your regular veterinarian may want to refer you to a surgical specialist. To find an ACVS veterinary surgeon in your area, click here: Find a ACVS Veterinary Surgeon
Exam, Screening Tests, Imaging
CCL rupture is usually diagnosed on physical and orthopedic exam. Joint effusion (fluid accumulation in the joint), fibrosis, muscle atrophy, decreased range of motion, popping (crepitus) or meniscal clicking of the knee on range of motion are all signs of CCL injury. A positive cranial drawer movement or cranial tibial thrust is diagnostic of the disease, however with partial ligament tears, early instability may be difficult to detect. Radiographs (x-rays) are usually taken to confirm joint effusion and presence of osteoarthritis, and to rule out concurrent disease conditions such as cancer (Figure 3).
Figure 3. A lateral radiograph of a stifle joint with effusion secondary to a CCL tear.
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Differential Diagnoses
Differential diagnoses for pain and lameness in the rear limbs of dogs include:
- long bone fractures
- joint luxations
- joint sprains or muscle strains
- patellar luxation -see the article in this section on patellar luxation to learn more about this disease
- hip dysplasia
- degenerative lumbosacral stenosis (cauda equine syndrome)
- degenerative myelopathy (a disease of the spinal cord)
- thoracolumbar disc disease (ruptured disc)
- bone or soft tissue neoplasia (cancer)
- panosteitis (an inflammatory bone disease seen mainly in young large breed dogs)
- tarsal instability
- Achilles tendon rupture
- osteochondrosis (a cartilage disease)
Complications Caused By The Disease
Common complications of CCL injury include:
- osteoarthritis (degenerative joint disease)
- meniscal tears
- loss of joint range of motion in the stifle
- muscle atrophy of the affected limb
- loss of athletic ability and full function of the affected limb
- rupture of the opposite cranial cruciate ligament.
Treatment Options
Broadly speaking, CCL injury can be managed either with conservative or surgical treatment.
Conservative treatment usually entails rest and nonsteroidal antiinflammatory medication for 6-8 weeks. Once the majority of pain and inflammation is resolved, then a conservative regime of exercise and weight loss (if necessary) should be initiated. Conservative therapy of CCL is best tolerated in patients weighing less than 15 kg. Results are more unpredictable in the larger animals. Given enough time, the lameness and pain often resolves within small patients managed conservatively. These animals appear to function normally on the injured leg; however, instability from the CCL injury persists and secondary degenerative joint disease inevitably develops.
Surgical treatment of CCL injury may be divided into two categories: extracapsular (outside of the joint) and intracapsular (inside the joint) techniques. The surgical treatment chosen is largely a matter of surgeon's preference, as several retrospective studies have shown that the success rate of any technique is near 90%, regardless of technique.
Intracapsular techniques attempt to stabilize the knee by replacing the ruptured CCL by passing an autologous tissue or synthetic graft through the joint (figure 4).
Figure 4. Arthrotomy with graft placement.
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There are varieties of intracapsular techniques available, which differ only in the placement of the graft. Most surgeons performing an intracapsular technique will often augment the repair with an extracapsular reconstruction. Some of the most common intracapsular techniques are:
- Over-the-top procedure
- Under-and over technique
- Paatasama technique
- Arthroscopic placement of a graft
Extracapsular techniques usually involve the placement of sutures outside the joint or redirection of the lateral collateral ligament. Another procedure, called the tibial plateau leveling osteotomy (TPLO) alters the biomechanics of the joint so the animal can bear weight and walk without a cranial cruciate ligament. The procedure, in particular, has a steep learning curve and should only be performed by a veterinary surgeon with advanced training. Some of the most common extracapsular techniques are:
- Lateral fabellar suture or retinacular stabilization (Figure 5)
- Imbrication technique
- Fibular head transposition (Figure 6)
- Tibial plateau leveling osteotomy (Figure 7)
Figure 5. Placement of a Lateral Fabellar suture for stabilization of a torn CCL.
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Figure 6. Radiograph of a dog following a Fibular Head transposition surgery for stabilization stifle with a torn CCL.
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Figure 7. Radiograph of a dog following a TPLO.
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Regardless of technique used to stabilize the stifle, the meniscus should be inspected for tears or other evidence of trauma or prophylactically released to prevent entrapment. Damage to the caudal body of the medial meniscus is seen in 50% to 75% of patients with a ruptured CCL.
Potential Complications Following Treatment
Complication following surgery will vary with the type of procedure performed, but in general infection, surgical wound problems, bandaging problems, implant failure, fracture, patellar luxation, and failure to return to function are the most common. Ten to fourteen percent of the patients repaired via an extracapsular technique may represent with meniscal injury at a later date. In addition 40-60% of the dogs will rupture the contralateral (opposite) CCL within one to two years following the initial presentation for lameness.
Aftercare
Most surgeons bandage the affected leg for 24-48 hours, regardless of the method of repair. Activity is restricted to leash walking for a minimum of 6-8 weeks. Supervised rehabilitation of the knee should start within 48 hours and should include a regime of passive range of motion, balance exercises, and walks on leash (figure 8).
Figure 8. Rehab of a yellow lab after TPLO surgery using a large ball for physical therapy.
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Swimming is also an excellent non-weight bearing activity, once the incision is healed. All therapies should first be cleared through your veterinary surgeon, prior to their implementation. Long term prognosis for animals with repaired CCL is good, with clinical reports of improvement in 85-90% of the cases. Unfortunately, degenerative joint disease or osteoarthritis progresses regardless of treatment. Long term outcome includes a decrease in activity over time, an increasing level of disability, an adverse response to cold weather, and stiffness after inactivity related to progressive degenerative joint. Weight loss and an exercise regime of daily moderate activity can help to ameliorate these clinical signs.
—Dianne Dunning, DVM, MS
Diplomate ACVS
Posted 8/13/2004
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