Cruciate ligament rupture
Cruciate ligament damage is one of the most common orthopaedic injuries in dogs. It normally presents with your dog becoming acutely lame in one of its hind limbs while running or playing. However, not all dogs have acute (sudden onset) lamness; they can present with gradual disuse of the affected leg. These patients often sit with their leg extended and have some muscle loss on the affected side. They may only have occasional lameness.
The cruciate ligament is one of several ligaments in the knee that allows the knee to act like a hinge. There are two cruciate ligaments: the cranial at the front and the caudal at the back. It is the cranial cruciate ligament that tends to suffer injury.
The anterior or cranial cruciate ligament (ACL) angles from the front of the tibia (shin bone) to the back of the femur (thigh bone), at the tibial plateau. The caudal cruciate ligament (CCL) angles in the opposite direction, crossing the CCL – hence 'cruciate' or cross.
When a dog runs or stops suddenly and the leg twists, the cruciate can rupture. There can be a full tear where the entire ligament is ruptured, or there can be a partial tear where only some of the ligament fibres are torn. Both types cause instability in the knee joint. This changes the biomechanics of the joint and if left untreated osteoarthritis sets in and continues until the dog can no longer use the leg in a normal manner.
How is it diagnosed?
Diagnosis is based on history, presenting signs and examination of the stifle – knee joint. If there is a full tear the dog has what we call a positive 'drawer sign'. This is when the vet can hold the thigh in one hand and the shin in the other and apply pressure to slide the tibial plateau under the femoral condyles. Another test is for 'thrust', which is a measure of dynamic instability and a good diagnostic aid. Both tests can be done on conscious patients without discomfort. However, in some cases it is better to perform the tests while the patient is under an anaesthetic.
If there is only a partial tear there is often no or less draw sign so partial tears can be harder initially to detect.
Definitive diagnosis is via radiographs. Several views are taken and we look for an 'effusion' or fluid in the joint. If there has been a partial tear for some time that the patient has not been presented for, there will already be some osteoarthritis in the joint. These dogs would have had a history of intermittent lameness that responded to anti-inflammatories but then returned with exercise.
At Sydney Animal Hospitals we take a standard series of radiographs that include both stifles (knees) and views of the hips.
How is ACL damage treated?
Repairing ruptured or torn cruciate ligaments requires surgery, in most cases. We have several surgical options and make a decision that is best suited to each presentation and patient.
Whilst anti-inflammatory drugs may provide pain relief and your dog may improve for a while, the joint is now unstable. If left, osteoarthritis sets in and will continue, eventually leading to a non-functional leg. Most dogs and cats with ACL injuries will spend some time on a non-steroidal anti-inflammatory drug (NSAID) before and after sugery.
There are several types of surgery and our surgeons will assess your dog and the radiographs and make a decision about the best procedure for your pet’s injury. Generally small dogs can undergo an extra capsular repair where a heavy suture is placed outside the joint to stabilse the knee. For medium to larger dogs a more complex procedure is possibly required. Larger and more active dogs often do not do well with stabilisation surgeries. These patients are recommended to have a procedure to stabilise the knee by changing the biomechanical function of the joint so a cruciate ligament is not needed for stability.
These procedures are performed regularly at Sydney Animal Hospitals. We use one of two techniques: TTO (triple tibial osteotomy), which is the latest technique to restore proper joint function; and the (tibial tuberosity advancement), which suits some patient presentations.
At the time of surgery the surgeon will also examine the knee for any damage to the other structures such as the menisci (internal cartilage) and surgically address these at the same time. The aim of surgery is to stabilis e the joint and prevent any further damage. Surgery is limited in reversing specific osteoarthritic changes that are already present, but surgery will in most cases improve significantly the long-term functionality of the joint.
How long is the recovery?
Post surgical recovery is about four to eight weeks. For the first four weeks the patient is only allowed to potter around the house and yard, with possibly short leash walks. After four weeks your dog can start to increase exercise on longer, slow lead walks. The surgeon will discuss the recovery plan at your discharge appointment. We have physical exercise programs that are needed to get the best recovery possible and details of these are given at discharge of your pet from hospital.
If your dog is overweight we will also work out a special diet as excess weight is a contributing factor to cruciate disease. Proper weight control is essential in recovery from any orthopaedic surgery.
If you have any questions regarding cruciate disease please contact any one of our Sydney Animal Hospitals clinics and speak to the veterinarian on duty.