Meniscal injuries in dogs are a common occurrence secondary to cranial cruciate ligament injury. Isolated meniscal injuries without a torn cruciate ligament are very rare, however.
The menisci are two C-shaped structures within the knee that play a role in distributing the force of weight-bearing from the femur to the tibia as well as act in stabilizing the femur on the tibia. The idea is that the bottom part of the femur is made of two round structures called condyles. The area that they contact on the tibia called the tibial plateau is a relatively flat surface. The menisci help allow a round surface to have more stability on a flat surface and increase the area available for weight-bearing.
Almost all of the time for the meniscus in the dog to be injured there has to be some laxity or tearing of the cranial cruciate ligament. When the cranial cruciate ligament is torn, this allows the femur to slide off the back edge of the tibia and then as it comes forward, grab a portion of the meniscus in the back of the joint and drag it forward, resulting in the torn piece sitting between the femur and tibia. The torn portion of the meniscus is almost always on the back half of the medial (inner) side of the joint.
Clinically, dogs with a torn meniscus show lameness, often severe, to the point of almost nonweight-bearing. Some of these dogs may have had a mild lameness before it suddenly worsened because the cruciate may have been slowly tearing long before the meniscus got injured. Another sign of a meniscal tear is a “popping” or “clicking” noise, called a meniscal click, when the dog walks. This is due to the torn portion of meniscus sliding around during movement of the joint.
Diagnosis of a meniscal tear is usually made by visual inspection at surgery. There are no known nonsurgical methods of repairing a meniscal tear and most dogs will ultimately not use the leg unless the torn portion is removed. Inspection of the meniscus can be performed using arthroscopy or via an arthrotomy (opening of the joint). Most of the time, the meniscus is being visualized along with some surgery to stabilize the torn cranial cruciate ligament. In dogs, attempts to repair the torn meniscus have not proven success. Therefore, removal of the torn portion of the meniscus is the standard of treatment. Other procedures like ultrasound and MRI of
the knee have been studied and may be effective at diagnosing a meniscal tear, but are rarely performed since surgery is usually indicated to repair the torn cruciate ligament anyway.
Meniscal injuries can also occur after a dog has had their knee repaired for a cranial cruciate ligament tear. This occurs in about 1 out of every 15-20 dogs and can occur months to years after the knee has been repaired. udden onset of lameness that does not improve with time or rest is the typical sign. These dogs will return to good use of the leg in most cases with surgical removal of the torn piece of meniscus.
Prognosis for dogs with meniscal tears is typically thought to not be as good in the long term as for dogs without meniscal injuries. Because the menisci play a role in stability and force distribution within the knee, an increase in post-op arthritis is expected after removal. Which procedure is performed to stabilize the knee may also play a big role in arthritis post-op. Clinically most dogs still do very well after meniscal removal and stabilization of the knee for the cruciate tear and if severe arthritis does occur, it is usually much later in life.