Cruciate Ligament Disease in Dogs
The cruciate ligament is within the knee joint, and has important functions in preventing abnormal movement of the joint. Abnormal movement of the joint causes pain and leads to development of arthritis.
The cruciate ligament can become damaged by an acute injury, such as a fall or sudden twisting motion. More commonly however, the ligament gradually degenerates and is then ruptured by a relatively minor trauma. It is not known exactly why this degeneration occurs, but it is often present in both knees, so it is not uncommon for a rupture to happen in the other knee within a year or so of the initial rupture.
There is no blood supply to the cruciate ligament, which means that it has a very limited ability to heal. Minor tears will sometimes heal if the forces acting on the ligament are reduced. Complete tears never heal, and the torn tissue sits within the joint causing further irritation.
When the ligament ruptures it is common for the cartilage pads within the knee, called the menisci, to become torn. These pieces of cartilage also do not have a blood supply and do not heal, so any damaged tissue needs to be trimmed away to alleviate the pain.
Cruciate ligament rupture is often strongly suspected at the initial examination, as we can often detect abnormal movement in the knee. To confirm the diagnosis however, we need to manipulate the joint with the dog anaesthetised when all the muscles are relaxed. We also take x rays to check for the changes in the joint that are normally associated with this injury, check for any other problems, and assess the anatomy of the joint and take measurements to help decide on the most appropriate treatment. Occasionally, particularly if the ligament is only partially torn, we are unable to completely confirm the diagnosis without looking inside the joint.
Tibial Tuberosity Advancement (TTA)
Cranial Closing Wedge Osteomy (CCWO)
The third surgical treatment we can perform a procedure known as ‘extracapsular stabilisation’. This involves placing a strong suture around the side of the joint, to hold the bones in position in relation to each other, mimicking the action of the ruptured ligament. This suture tends to stretch and loosen over time, but fibrous tissue will form around the joint before this happens, generally resulting in a fairly stable, but often stiff joint. This procedure can give a reasonable functional outcome in some dogs, but in others (particularly dogs over 25kg or some terrier breeds) the forces acting on the knee joint means that excessive pressure is placed on the suture and inadequate stabilisation will be achieved. Occasionally, the suture will snap before enough fibrous tissue has formed, necessitating another operation to fix this.
Whichever surgical procedure is performed, the joint will also be opened up and examined, to remove any pieces of damaged ligament or meniscus.
Dogs vary massively in the shape of their bones and joints, and their athletic ability and expectations, and our vet will discuss this with you and provide advice on the most appropriate treatment for your dog.
All surgical procedures do inevitably carry risks. With all of these procedures there is a risk of infection developing, which can be serious if it affects the joint or implants. We take precautions to reduce the risk, including strict sterility during the procedure, antibiotics during and sometimes after the procedure, and use of an Elizabethan collar to prevent chewing of the wound. Another risk with these procedures is failure of the implants, which will sometimes require another
operation. This can potentially be more serious with the TTA and CCWO procedure than with the extracapsular stabilisation. Exercise restriction for 6-8 weeks is required after any of the techniques to reduce the risk of the implants being overloaded and failing.
After an operation for cruciate ligament rupture, dogs will usually stay at the practice until about 6pm to receive several doses of injectable pain relief, and are usually able to go home that night with oral pain relief.
Your vet will be happy to discuss any of these points with you further, and answer any questions you may have.