What is the canine Cruciate ligament and what does it mean to have a rupture?

The canine cruciate ligament is similar to the anterior cruciate ligament (ACL) in people. It stops the shin bone (tibia) moving forwards relative to the thigh bone (femur) and prevents internal rotation of the knee. It has two components which work together to stop the tibia moving when the knee (stifle) is both flexed (bent) and extended (straight). In dogs it is generally considered to be a degenerative condition due to the angle of the joint being too steep. It can also be traumatic as it is in sportspeople however this is less common for dogs.

As there are two components to the cruciate ligament in dogs, they can have either a partial or complete rupture of their cruciate ligaments. Unfortunately a partial tear is almost certain to become a full tear in the future as the remaining band will face more inappropriate forces and the knee will become unstable when flexed.

Dogs that have suffered a cruciate rupture are typically very sore at the point of the injury or immediately afterwards but the pain may lessen with time and rest. They may be reluctant to put their foot down on the affected leg, or in some cases they will be toe-touching (putting the foot on the ground but not actively weight bearing). Although some very stoic dogs will also be able to walk/run around with some lameness.

Some unlucky dogs also tear their meniscus (a pad of cartilage in the joint), as the knee is now unstable and moves in ways it wasn’t intended to. This is generally much more painful.

Treatment options for cruciate disease

When your pet is diagnosed with a cruciate ligament rupture the initial therapy is anti-inflammatories, pain relief and rest. The immediate goal is to reduce ongoing trauma to the joint due to inflammation and instability. With time the inflammation and swelling within the joint will reduce and the knee will fibrose (scar) to provide more stability. For some dogs this method of conservative management is a good option, however for dogs larger than 15kg this rarely results in a return to function for that leg.

Surgical intervention is the preferred option and there are a variety of procedures available that work. With advancements in veterinary medicine the techniques that attempt to replicate the function of the ruptured ligament are considered less favourable compared to procedures that eliminate the need for the ligament. The procedure performed here at Hollybank Vets by our resident Professor in orthopaedics Rob Pettitt is called a tibial plateau levelling osteotomy (TPLO).

The TPLO means we change the angle that the tibia sits at relative to the femur which prevents the forward movement of the tibia when the leg is loaded. This requires radiographic (x-ray) measurements of the knee and proper planning of the intended bone cuts. Once the angles have been measured we are ready for surgery.

The first part involves opening the joint and inspecting the cartilage, ligaments and menisci. This enables any meniscal tears to be removed and confirms there isn’t any other underlying disease process. Then a semi-circular bone cut is performed through the top of the tibia, rotating the fragment before fixing it with a locking/compression plate as we would for a fracture. This may sound excessive or unpredictable however the benefits of this procedure are very repeatable and predictable outcomes. Whilst the bone cut is healing the pet must be rested to allow the bone to heal however after 8 weeks they will graudally start to increase their exercise and by 16 weeks we expect a normal return to function.

Long term outcomes for surgical repair are more favourable than conservative management, however as the joint has sustained an injury it will suffer from osteoarthritis. Unfortunately as this is largely a degenerative condition if a dog suffers one cruciate injury they are likely to suffer another in the other leg. Ongoing weight management and exercise management often help mitigate this risk and by maintaining a good weight in a well muscled dog we are more likely to see better outcomes.

Professor Rob Pettitt

We are very fortunate to have Rob here at Hollybank, he works at our Winnington surgery on a Friday and is open to reviewing all dogs (and cats) with cruciate ligament disease or any other orthopaedic disease.

Rob started his career as a sailor in the royal navy before jumping ship to become a veterinary surgeon.

Rob graduated from the University of Liverpool in 2002 and spent three years in general practice. He returned to the University as a Clinician Teacher in Small Animal Orthopaedics and in 2010, passed the RCVS Diploma in Small Animal Orthopaedics. Rob is now an RCVS recognised specialist in orthopaedics, has published widely in his field, is the current chair of AOVET principles course and has presented at numerous conferences both nationally and internationally.

Rob continues to work as Professor of Small Animal Orthopaedics at the University of Liverpool but joined the Hollybank team in addition to this in 2024. Rob provides specialist orthopaedic consultations and surgeries at our Winnington practice . Our Orthopaedic service is supported by our own vets and RVNs whom Rob also provides additional support and teaching to.

Outside of work Rob is a keen cyclist and enjoys exploring the local area.

If you think your pet may be showing signs of joint disease or you wish to know more about this condition please contact the practice on 01606 880890 or 01606 717969