Cranial Cruciate Rupture in Dogs

What is it?

The knee is a complicated joint; comprised of the femur above, tibia below, patella at the front and a small bone called the fabellae behind the joint. The joint itself is made up of two cartilaginous structures called the menisci, as well as multiple ligaments that allow the joint to function as it should. There are two ligaments which cross over inside the knee joint – the cranial and caudal cruciate ligaments. These form an ‘X’ within the joint, and keep the knee stable by preventing the femur from sliding too far forwards or backwards on top of the tibia.


The cranial cruciate ligament is the most common rupture that occurs in dogs. It may be a full or partial tear, and may occur slowly over time (often seen in older, large dogs) or as one sudden incident (often seen in active, young, large dogs). This ligament prevents the femur from sliding backwards, so once ruptured, the knee is no longer stable and the dog is unable or reluctant to bear weight on that leg. If left untreated, especially in large dogs, significant osteoarthritis will develop and return to normal function is unlikely.

How is it Diagnosed?

In order to diagnose a cruciate rupture, the dog will need to have a thorough assessment under sedation or general anaesthesia.

The Drawer Sign: this may need to be performed while the dog is asleep, to allow for more muscle relaxation. This is a test where the veterinarian will stabilise the femur and attempt to slide the tibia forward. If the cranial cruciate is intact, the tibia should not be able to move forward. When the cruciate is ruptured, stretched or partially torn, the tibia is able to move forward as shown by the red arrow in this image.

Radiographs: Radiographs of the knee are then taken, both for surgical preparation and to determine the extent of damage from the cruciate rupture. The veterinarian will be looking for signs of swelling within the joint, as well as bony changes that may have occurred due to the cruciate rupture.

What can be done?

Surgical repair is usually recommended. Unfortunately, 50% of dogs with a cruciate rupture are at risk of rupturing the other cruciate in the future. It is important to return the patient to normal weight bearing as soon as possible, to reduce the risk to the opposing leg. Many dogs also have damage to the medial meniscus, which can only be effectively assessed during the surgery. The damaged portion can then be removed.

The ideal surgical methods aim to alter the angle of the tibia to prevent the forward movement, which allows the ligament to stabilise over time, and provides immediate relief of the joint instability, allowing the dog to bear weight on the limb. This will reduce the development of osteoarthritis within the joint, although some arthritis is inevitable and will be managed in the post-operative care. Our surgeries are performed by an experienced surgeon, who will perform a Tibial Plateau Levelling Osteotomy (TPLO) for a large dog, or a Tibial Wedge Osteotomy (TWO) or Modified De Angelis for smaller dogs. Further information on these procedures can be found at

What if surgery isn’t an option? If surgery cannot be performed due to financial or medical constraints, then conservative management is recommended. This is aimed mostly at managing the development of osteoarthritis, similar to the aftercare outlined below and in the attached ‘Joint Health’ information sheet.  

What should I expect after surgery?

Post-surgical care is extremely important in the success of cruciate repair surgery. Your dog will be able to bear weight on the leg very soon after surgery. While this is good for appropriate healing, it must be strictly controlled as your dog will feel much more stable and want to run around more than is safe.

  • Confinement: The dog must be confined for a minimum of 6 weeks after surgery. You must be prepared to crate your dog, or confine them to a small room with non-slip flooring. If your dog is not used to confinement, you may like to start training your dog to use a crate before the surgery.
  • Controlled exercise: No jumping, running or stair climbing is allowed. Only short on-leash walks to the toilet for the first 3-4 weeks as advised. After this time, light activity can be increased, such as a controlled walk around the block.
  • Enrichment: We understand it can be very difficult to confine a highly active and/or highly intelligent dog. To give your dog the best chance of success, you can entertain your dog with other enriching activities that do not include exercise. This can include items such as Kong’s stuffed with food, scent games, snuffle mats, training simple non-strenuous tricks, slow ‘scent walks’ allowing your dog to sniff, and many other options.  

Osteoarthritis management: This includes supplements to support joint health, weight loss if required, diet modification, omega 3’s, acupuncture, physiotherapy, laser therapy and joint support injections. Both laser and joint support injections (Synovan) are included in the price of the surgery. Please see the attached ‘Joint health’ information sheet for further details.

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