Within the stifle, or knee, joint there are two menisci, which are C-shaped structures made of cartilage. The menisci sit on top of the tibia, and act as a cushion to disperse force and friction the knee joint.
Dog of any age, breed, or gender can sustain meniscal injuries. Dogs with rupture of the cranial cruciate ligament are prone to concurrent meniscal damage.
Usually, dogs with meniscal injury along with cruciate tears have more pain and lameness than with a cranial cruciate rupture alone. Often there is a history of improving lameness after the cruciate rupture, followed by worsening as the meniscus subsequently is injured by the instability. Sometimes the owner can hear a “click” in the knee of a dog with meniscal injury when the dog walks, and is caused by the movement of a free section of the torn cartilage.
Because damage to the meniscus usually goes along with a cranial cruciate rupture, and complete and accurate diagnosis is essential. After rupture of the CCL, and many as 53% of dogs sustain meniscal injuries. Diagnosis is based on a physical exam, during which the veterinarian may hear or feel a click or a grating sensation when flexing, extending, or testing the stability of the knee. Radiographs are usually not helpful in diagnosing meniscal tears, but should be performed to fully evaluate the stifle and rule out other causes of lameness. Other methods of diagnosis, which are more accurate, include ultrasound, MRIs, and arthroscopy.
In dogs, most meniscal injuries are a secondary to cranial cruciate ligament ruptures. When the CCL is
torn, the tibia is displaced cranially; as a result, when the joint moves, the femur slides and rubs against the meniscus, causing damage to the cartilage. The meniscus can also become wedged between the tibia and femur, and gets crushed when the dog is bearing weight on the affected leg and the joint is extended. However, isolated meniscal injuries do occur, usually when the dog sustains a fall during which the leg is twisted.
Medical management is not an option with meniscal because the constant back-and-forth sliding of the torn meniscus causes severe pain that will not improve with conservative management and accelerates degenerative joint disease. Therefore, surgical repair of the damaged meniscus is required.
The most important way to prevent meniscal injuries is to have your dog examined by a veterinarian promptly after signs of lameness appear. Early diagnosis and surgical repair of a cranial cruciate ligament rupture results in a much lower incidence of meniscal injury. One method of repair is primary repair of a torn meniscal body, which involves suturing the meniscus back together. Another option is partial meniscectomy, in the damaged section of cartilage is removed. This technique is often the treatment of choice, especially due to the difficulty in placing sutures in the meniscus in dogs, as in a primary repair. In very severe cases, the entire meniscus may need to be removed.
Partial meniscectomy or primary repair of the damaged meniscus is usually good, and these procedures lessen the degree of degenerative joint disease (DJD), which makes the prognosis for return to normal function more favorable. However, total meniscectomy may promote DJD and is generally avoided. Dogs with meniscal injury associated with CCL rupture have a poorer long-term outcome than dogs with CCL rupture without meniscal injury. Additionally, the use of a chondroprotective agent containing polysulfated glycosaminoglycan, such as Adequan®, has been shown to significantly improve the overall health of the joint cartilage.