03/05/2024
Here we are sharing some useful information about one of the most common causes of hind limb lameness in dogs:
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 heavily sedated or 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.
Cruciate ligament injuries are sometimes managed without surgery. This can result in a reasonable outcome in some smaller dogs, but arthritis in the joint will continue to progress. The hope is that sufficient fibrous tissue will form around the joint to reduce the abnormal movement, but will inevitably mean that the joint becomes stiff. In bigger dogs it is far less likely that the joint will have acceptable function without surgery, and they are likely to be left with a painful knee.
Fiona performs the following procedures at our practice:
Tibial Plateau Levelling Osteotomy (TPLO)
The operation that we most frequently perform for treatment of cruciate injury is a procedure called tibial plateau levelling osteotomy or ‘TPLO’ for short. This involves making a partial circular cut in the bone just below the knee, rotating the segment that has been cut, and securing it in place with a metal plate and screws. The theory behind this procedure is that the forces acting on the knee will be altered to negate the need for an intact cruciate ligament. If there is only a partial tear, this procedure can reduce the pressure on the ligament enough to prevent further tearing, and possibly allow some healing. This procedure is considered by many experts to be the best treatment for cruciate rupture for the majority of dogs.
Cranial Closing Wedge Osteotomy (CCWO)
Another surgical option that we offer is a procedure known as cranial closing wedge osteotomy or ‘CCWO’. This is most commonly recommended for small breed and terrier type dogs and involves cutting a wedge out of the bone below the knee joint and fixing this with a plate, the objective being to change the shape of the bone and as in TPLO, to negate the need for an intact cruciate ligament.
Extra-capsular Stabilisation
The third surgical treatment we can perform a procedure known as extra-capsular 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.
Dogs vary massively in the shape of their bones and joints, and their athletic ability and expectations. Fiona can discuss this with owners and provide advice on the most appropriate treatment for their dog.
