What is a Torn Knee Ligament in a Dog?
A torn knee ligament in dogs, also known as a stifle, involves a complex structure comprising various bones such as the femur (thigh bone), patella (kneecap), and tibia (shinbone), along with ligaments and the meniscus. Typically, when discussing a torn knee ligament in dogs, it refers to the tearing of the cranial cruciate ligament, which is akin to the anterior cruciate ligament (ACL) in humans. This ligament plays a crucial role in stabilizing the knee by preventing excessive sliding of the tibia in front of the femur. When the cranial cruciate ligament ruptures, it compromises the stability of the knee.
The severity of lameness observed can vary depending on the extent of damage to the ligament, whether it’s a partial tear or a complete rupture. Over time, the condition may worsen as the ligament deteriorates and affects other internal knee structures. It’s noteworthy that around 50% of animals that experience a torn ligament and rupture in one knee are likely to encounter a similar issue in the other knee at some point in the future.
Symptoms
The primary symptom indicating torn knee ligaments in dogs is hind-leg lameness. The severity of lameness can range from occasional limping after activity to an inability to put weight on the affected leg. Additionally, when sudden full or partial tears happen, you might observe swelling or discomfort when touching or moving your dog’s knee.
Causes
Torn knee ligaments in dogs can stem from two main causes. Firstly, the cranial cruciate ligament (CrCL) undergoes wear and tear over time, resulting from physical activities and stress placed on the knee. This gradual deterioration is known as cranial cruciate ligament disease (CrCLD) and usually progresses over months to years. Factors contributing to CrCLD include breed, aging, obesity, genetics, and poor knee structure. The accumulation of damage eventually leads to ligament rupture during regular use.
The second cause involves a sudden traumatic rupture of the CrCL, which occurs due to a specific incident such as being struck by a vehicle or engaging in rough play at a dog park. This type of rupture is uncommon and typically affects young, healthy dogs whose ligaments have not sustained prior damage.
Diagnosis
Veterinarians diagnose a fully torn cranial cruciate ligament (CrCL) by identifying cranial drawer, which indicates instability in the knee. This instability is evident when the veterinarian manipulates the knee and is present only when the CrCL is completely torn.
To assess cranial drawer, the veterinarian will grasp the thigh bone and shin bone and attempt to pull the shin bone in front of the thigh bone. An intact CrCL will prevent the shin bone from moving past the thigh bone. Sedation might be necessary for proper radiographs and evaluation due to the strength of the muscles around the knee and the pet’s compliance.
If cranial drawer is absent, it indicates that there isn’t a full tear to the CrCL. The veterinarian will also observe the dog’s gait while walking, check for joint effusion (accumulation of extra fluid in the joint capsule), and look for signs of pain during knee manipulation. Radiographs (X-rays) are usually required to evaluate internal knee structures, assess joint effusion or arthritis severity, and plan surgery, if necessary.
There are three surgical options for correcting a torn knee ligament in dogs:
- Extra-capsular suture stabilization: This procedure involves placing a nylon monofilament suture material outside the joint capsule to replace the torn CrCL. It’s suitable for smaller, less active dogs.
- Tibial plato leveling osteotomy (TPLO) and Tibial Tuberosity Advancement (TTA): These procedures involve cutting into the tibia and using screws and bone plates to stabilize the knee without relying on a functional CrCL. They’re recommended for active, young, or large breed dogs.
Your veterinarian may also recommend medications post-surgery to manage pain and inflammation, such as anti-inflammatories, sedatives, Adequan injections, and joint supplements.
Physical therapy and follow-up treatment are crucial for your dog’s recovery. Discussion with your veterinarian or surgeon will help determine the best procedure based on factors like size, activity level, knee stability, age, and finances.
Recovery and Management
After surgery, lameness typically persists for about a month but gradually improves over time. Proper healing requires a strict regimen of three to four months of cage rest, during which the pet should remain confined to a small room or kennel, except for short leash walks for bathroom breaks, spending time with family, or eating. Any unrestricted activity should be closely monitored by a family member to prevent excessive use of the affected knee, which could lead to surgical complications or procedure failure.
It’s crucial to avoid slippery surfaces and sudden changes in elevation, such as stairs or getting on and off furniture. Following the initial rest period, a gradual increase in limb workload is advised, aiming for full recovery and limb usage within six months.
Torn Knee Ligament in Dogs FAQs
Can a dog recover from a torn ligament without surgery?
While a dog can continue living with a torn ligament, without surgical correction, arthritis and hind leg lameness in the knee are likely to progress.
Can a dog's partially torn ligament heal without surgery?
Unfortunately, a partially torn CrCL will not heal on its own due to the poor blood supply to the ligament.