In dogs, one of the most common orthopedic injuries is a cranial cruciate ligament (CCL) tear — this is comparable to when a human injures their anterior cruciate ligament or ACL. Injury of the CCL may be caused by a traumatic event, or by degenerative cranial cruciate ligament disease. Multiple factors contribute to this disease process including aging or degradation of the ligament, obesity, poor physical condition, genetics, breed, and skeletal shape and configuration. Unfortunately, 40-60% of dogs that develop cranial cruciate ligament disease in one knee will eventually develop it in the other as well. It is also important to note that partial tearing of the CCL almost always progresses to a full tear over time.
The cranial cruciate ligament is one of the most important stabilizers in the canine knee (stifle). When the CCL ligament is compromised, the knee joint is unstable, and the shin bone (tibia) slides forward, with relation to its normal position with the thigh bone (femur). This displacement is often referred to as “cranial drawer,” as the tibia’s movement is similar to how a drawer slides out. This causes discomfort and can lead to lameness and dysfunction. Over time, this instability can also result in damage to the cartilage and degenerative joint disease (osteoarthritis).
The meniscus is a “cartilage-like” cushion that sits in between the tibia and femur. It serves many important purposes in the joint such as shock absorption and load bearing, and it can be damaged when the CCL is torn. This may lead to increased pain within the knee joint.
Signs that may indicate your dog has experienced a CCL injury may include limping (lameness) on a back leg, stiffness after rest, generalized decrease in activity level, unwillingness to play or jump up, muscle loss in the affected leg (atrophy), firm swelling on the inside of the shin bone (medial buttress), etc. If a clicking or popping noise is heard from the knee, it may indicate the presence of a meniscal tear.
Veterinarians can help confirm diagnosis of CCL injury via history, clinical signs, exam findings, and x-rays (radiographs) of the knee joint.
So now what?
At Mission Animal Hospital our doctors and board-certified veterinary surgeons will work with pet parents to decide the right course of action. Surgery is typically the best treatment option for CCL injury because it is the only way to reliably control the instability present in the knee joint. One possible surgical treatment is “TPLO surgery”. TPLO stands for Tibial Plateau Leveling Osteotomy.
Unlike in human ACL surgery, the goal of veterinary surgery is not to repair or replace the damaged ligament. Instead, the TPLO changes the way the quadriceps muscles act on the top of the shin bone (tibial plateau) and stability of the knee joint is achieved by a change in the overall biomechanics. Once a TPLO has been performed, the abnormal sliding movement of the tibia, with weight bearing, is eliminated.
What happens during the surgery?
The very first step of surgery is to confirm diagnosis by thorough examination of the knee joint. The torn portion of the CCL will be cut away (debrided) to minimize inflammation in the knee joint. If a meniscal tear is concurrently identified, the damaged portion of the meniscus will also be removed to improve overall comfort.
Then, a semicircular bone cut (osteotomy) is made in the top of the tibia. The tibial plateau is then rotated to create a near level surface at the top of the bone. This change in the bone position is held stable with a specialized orthopedic plate and screws. By “leveling” the top of the tibia, the surgeon creates a configuration of the knee where it is more stable. In fact, instability is evaluated in surgery to ensure that it has been corrected.
Post-operative radiographs are taken to confirm appropriate placement of the surgical implants and that the desired tibial plateau angle has been achieved.
What can you expect during the recovery?
Activity restriction (for 8-12 weeks):
For the first 24 hours following the procedure, TPLO patients may be a bit groggy and unsteady on their feet. Therefore, in an effort to prevent stumbling or falling, it is advised to confine them to a comfortable, safe, indoor location without free access to stairs or slippery floors. If necessary, a sling (placed under the abdomen, in front of the hindlimbs) or body harness may be used to support the hind end during ambulation until they are walking with more confidence. For the first 2 weeks, patients are limited to short, controlled, leash walks for elimination purposes only. Following that time, a gradual increase in the duration of walks is allowed. Professional rehabilitation, swimming, and other low-impact activities can be helpful during recovery but are typically prescribed on a case by case basis.
Throughout the recovery period and until radiographic healing of the bone has been documented (usually at 8 weeks), running, jumping and rough play should be prevented. The surgeon will help with tips and tricks to achieve these goals as premature, uncontrolled or excessive activities risk damage to the surgical repair!
Care of the Surgical Site/Incision:
A light dressing is typically placed to protect the incision post-operatively. This should remain in place for 24-48 hours and then may be removed. After bandage removal, the incision should be monitored closely for signs of infection. Signs include increased redness, swelling, drainage, or separation of the wound edges. It is very important to prevent licking and chewing of the incision. An e-collar (or cone) should be used to prevent this behavior while the incision heals (2 weeks).
Following surgery, there will be swelling over the knee joint. Do not be alarmed if this swelling moves to the ankle region (tarsus) with time. The swelling, and any redness or bruising, should resolve in about 5-7 days.
2 weeks: Evaluation is typically performed 2 week post-operatively to assess the incision for healing and to remove any skin sutures or staples that were placed. At this time, an orthopedic exam will also be performed and recommendations for ongoing activity restrictions will be made (a specific week by week plan will be outlined by the patient’s care team).
8 weeks: Radiographic assessment is performed at 8 weeks post-operatively to assess bone healing and the surgical implants. At this time, most patients have enough healing and muscle recovery (strength and endurance) to gradually return to normal activity over the following 4 weeks. By 12 weeks, most patients are back to their normal routine!
What is the outcome?
For most dogs, this surgery is highly successful! After the healing period, the improved overall stability of the knee will reduce discomfort and ongoing damage to the joint. With diligent aftercare, the majority of patients will resume normal function and previous activities. The perceived advantages of TPLO, compared to conservative measures and suture-based surgical techniques, are the superior outcome obtained with regard to limb function and athletic ability, with less progression of osteoarthritis.