Canine cruciate ligament disease

Unlike the fairly flat human knee, the dog knee has a steep internal slope which makes the cruciate ligament vital for its stability. The steep angle and associated forces means that when this ligament starts tearing it usually continues to a full rupture over time.

In the majority of dogs there is an underlying degenerative process that results in the ligament weakening with age. For this reason when a pet tears one ligament the opposite leg is often affected soon after. Most cases are seen around five to seven years when the ligaments are weakening but the dog is still very active.

Dogs of all sizes are affected but the arthritic damage from knee instability occurs faster and more severely in larger breeds.

Delaying desexing in larger breeds until a year of age may reduce future risk of this condition.

A cruciate ligament tear often presents with a mild persistent lameness in a hind leg that flares after activity and persists despite medical treatment and rest. This usually indicates a partial tearing of the ligament with more tearing and inflammation occurring with ongoing activity.

This is the best time to make a diagnosis before the joint becomes unstable as less damage to the joint has occurred and better outcomes can be achieved with surgery, especially with the TPLO procedure.

At the other end of the spectrum dogs can present with a complete ligament rupture and very poor use of their leg.

With a complete cruciate rupture, if the dog is not too uncomfortable, the vet may be able to palpate an instability. Often there will be more joint fluid or swelling than the unaffected leg. In some dogs there may be a click as the knee joint moves indicating a meniscal cartilage tear also, which is another important structure in the knee.

Many cases however will be much more subtle and harder to confirm. An anaesthetic and X-rays are indicated to rule out other painful conditions, assess for arthritic changes and confirm the diagnosis before the big step of a surgical recommendation. If surgery is indicated then well positioned X-ray views of the knee will be needed for pre surgical software planning.

Since a ruptured cruciate ligament creates an unstable and unhappy joint it is logical that providing surgical stability is ideal. For some pets this may not be the right management for them however.

If your pet is very old and already has substantial arthritis or a long surgery is not possible due to disease such as heart failure then surgery may not be the correct choice. Finances may not permit an advanced and technical procedure. Some smaller breeds under 10 kg can do quite well with conservative treatment as less extreme force is generated through their knees.
If surgery is not done some stability through scar tissue forming ( periarticular fibrosis) will partially stabilise the joint over 3-6 months. There will be more arthritis that will need ongoing management. The joint will likely have a reduced range of motion and some muscle loss.
Canine Rehabilitation can be very helpful in these cases

The TPLO ( Tibial Plateau Levelling Osteotomy ) is currently considered the gold standard surgical treatment as it appears to provide superior knee stability in the highest proportion of dogs. A study indicated less progression of arthritis after a year than the TTA procedure. This is the procedure chosen by most specialist surgeons.

If a patient has an early partial ligament tear and it is still competent, it will often be left in place with this procedure, as the excellent stability achieved may stop further tearing. This can create the best possible outcome and reduce the risk of future meniscal tears.

This procedure can be done in most sized dogs these days. It is also ideal for dogs with slopes too steep for the TTA.

This procedure is the most technically challenging and therefore the most expensive option.

The surgery involves making a carefully measured curved cut in the bone at the top of the tibia ( just below the knee) and rotating this to change the slope of the knee to a more neutral angle of about five degrees. Dogs often have a steep starting slope of 24 to 30+ degrees. With the forces on the knee neutralised the ligament is no longer needed. A specifically designed locking bone plate and screws holds the bone in its new alignment while healing.

We use special orthopaedic software to preplan each surgery. Success rates with this surgery are reported at over 95%.

The TTA ( Tibial Tuberosity Advancement) is another excellent surgical option with high success rates especially when compared to the extracapsular repair option. As stability may be a little less in some cases than the TPLO there may be a greater risk of future meniscal tears. In our experience this has still only been about 5% of cases however. A meniscal cartilage tear can cause lameness resulting in the need for a further joint surgery.

This procedure is best reserved for knees with a slope of less than 27 degrees. The surgery does not require a cut right through the bone like a TPLO but does require a cut through the bone at the front edge of the tibia. Potentially this means less surgical risk if something goes wrong.
The standard procedure which we have found to be very successful uses a cage and plate with screws to hold the cut bone, that’s moved forward to a new position, while it heals. This procedure has had reliable healing even in senior patients.

There are a number of variations of this surgery that try to simplify it by using a titanium wedge which unfortunately would be very difficult to remove if a problem arose.

This procedure does have a very fast recovery time to relative comfort after surgery in most cases but only a bit more so than the TPLO. The slowest recovery is with the extracapsular repair. This procedure is a bit more affordable than the TPLO

This is the original surgery for this condition and is the least technical and most affordable.

It involves placing an implant such as thick nylon or a multifilament fibre material across the outside of the joint to try and physically stabilise it. These implants often broke or loosened prematurely in large active dogs resulting in a return of instability and greater development of arthritis. The surgery largely relies on scar tissue as happens with no surgery to stabilise the joint long term.

The procedure can be clinically effective in most small breed dogs though has been superseded by the TPLO and TTA in larger dogs. Recovery with this procedure is slower than with the TPLO and TTA.

The meniscus is a “C” shaped structure inside the knee. There are a pair of them that act as shock absorbers protecting the cartilage and acting as an interface between the rounded end of the femur and the flat top of the tibia bone.

The medial meniscus on the inner side of the knee is often damaged when the cruciate ligament tears. When the knee is unstable extra force runs through the medial meniscus which can result in a tear or split usually in the rear hidden portion of the meniscus.

When this damaged portion flicks forward when walking an audible click may be heard in some dogs. The dogs with meniscal tears can be especially lame.

It is important during surgery to carefully check for these tears and trim away the damaged portion. A small percentage of these tears can be missed even with careful assessment.
One of the frustrating issues with the meniscus is when a tear occurs some time after surgery. These late meniscal tears can occur in about 5% of surgical cases and may necessitate a further surgery to treat. This can be months or years after the original procedure.