Published September 3rd, 2026

By Eva Groesbeck DVM, CVA, Grad Dip VCHM, CVMMP, FFCP, LMT, CVNN, CRPM

What is Cranial Cruciate Ligament Disease?

Cranial cruciate ligament dysfunction is the leading cause of rear-leg lameness and knee pain in dogs, affecting roughly 3-5% of all dogs. It most commonly affects large- and giant-breed dogs, but can also occur in small- and toy-breed dogs and cats. But what really occurs in patients with cruciate disease, and why has it become so prevalent in our canine populations?

First, we have to understand what ligaments are and what their function is in the body. Ligaments are tough, flexible fibrous bands of connective tissue that connect one bone to another. Built mainly from strong collagen fibers and some elastin, this gives them high tensile strength with slight flexibility. These fibers are arranged in taut, parallel bundles to allow them to handle heavy pulling and mechanical stress. By holding bones in their proper alignment, they provide joint stability and prevent abnormal or dangerous movements, guide normal joint motion, and stop dangerous movements such as overextension or dislocation of a joint.

The cruciate ligaments are two strong bands of tissue located inside the center of the knee joint that cross each other to form an "X" shape and connect the thighbone (femur) to the shinbone (tibia). The cranial cruciate ligament is located in the front part of the center of the knee and is the ligament that is damaged in patients with cranial cruciate disease. Its job is to stop the shinbone from sliding too far forward under the thighbone and also to provide rotational stability.

In the 1980s, veterinarians began to recognize that the vast majority of cruciate injuries were not the result of a sudden accident or trauma, but rather the result of a slow, chronic degeneration of the ligament matrix that occurred over months to years.

The cranial cruciate ligament is composed of two bands, the craniomedial band and caudolateral band. The craniomedial band is the front part of the ligament, and it stays taut during all knee movements, making it more susceptible to early degenerative changes and microtears. Enzymes called matrix metalloproteinases then act to break down the collagen fibers inside the ligament, weakening its structure over time. Meanwhile, inflammation develops in the lining of the knee joint (synovium) and accelerates tissue damage and matrix breakdown. As microscopic damage to the ligament accumulates, the weakened ligament eventually fails and ruptures completely under the strain of normal daily activities.

This progressive breakdown of the main stabilizing ligament in the knee eventually leads to joint instability, pain, a risk of meniscal damage, and the development of arthritis. This is the condition we commonly call cranial cruciate ligament disease.

Why is it so commonly diagnosed?

Prior to the 1980s, cranial cruciate ligament disease was a relatively uncommon phenomenon that was diagnosed much less frequently than it is today. This begs the question: Why? In my opinion, a combination of factors has contributed to an actual increase in the incidence of this disease. But simultaneously, veterinarians also became more aware of the condition and thus were more likely to screen for it and diagnose it. So, in essence, the disease is both occurring with greater frequency, and we are diagnosing it more because we are looking for it. The following conditions all had a notable impact on the increased frequency of this condition.

• Poor breeding practices and resultant conformational changes, which altered biomechanics and increased stress on the joint and ligament

• Development of a sedentary lifestyle for the modern pet

• The pet obesity epidemic

• A dietary shift to highly processed feeding practices

• Hormonal changes secondary to early spay/neuter initiatives

• The profession became more aware of the chronic nature of the condition and more prone to screen pets for signs of disease

• The development of the TPLO procedure created a monetary incentive to recognize the condition and recommend surgical intervention

• Over time, veterinarians have been trained to develop tunnel vision, assuming that all hind-leg lameness must be due to cruciate disease unless proven otherwise which may result in the over-diagnosis of this condition

Risk Factors for Cranial Cruciate Ligament Disease:

• More common in large- and giant-breed dogs

• Genetic predisposition; overrepresented in certain breeds, such as Labrador Retrievers, Rottweilers, Newfoundlands, Staffordshire Terriers, Boxers, etc.

• Age: Middle-aged dogs, 6-9 years old, are most commonly affected

• Spayed or neutered, especially if sterilized prior to 1 year of age

• Anatomy/Conformation: straight rear legs, steep tibial plateau slopes

• Sex: females show a higher statistical incidence

Diagnosis:

Diagnosis typically relies on physical evaluation of the knee joint, including a manual "cranial drawer test" or "tibial compression test" to assess for abnormal cranial motion of the tibia, which suggests damage to the cranial cruciate ligament. Most veterinarians would lead you to believe this test is highly diagnostic, but in reality, it is a clinical assessment and only about 60% accurate.

X-rays of the knee are also commonly taken to screen for other potential causes of lameness and to look for radiographic signs that support a diagnosis of cruciate ligament disease. However, the cruciate ligaments are not visible on an X-ray, and you cannot directly assess their integrity from X-rays.

In human medicine, an MRI is the gold standard for diagnosing cruciate disease and is routinely ordered early to clearly visualize the extent of ligament damage and check for associated meniscal damage. Unfortunately, this practice is not standard in veterinary medicine, largely due to the associated costs and limited availability of advanced imaging, so we frequently do not have the full picture in terms of what is actually occurring within the joint.

In situations where partial tears are suspected or in ambiguous cases where the diagnosis is uncertain, dogs are often subjected to invasive arthroscopy or surgical joint exploration to visually inspect the ligament and joint structures.

Treatment Options:

Surgery:

The general consensus in the veterinary world is that surgery is the best option for dogs with cranial cruciate disease. However, there are a number of things to consider before jumping into a costly and invasive surgery.

Body Weight: Dogs that weigh 33 pounds or less and cats all have a high success rate of recovery with conservative treatment measures without surgery. If you are being advised to have cruciate surgery performed on a cat or a dog under 33 pounds, consider getting a second opinion and ideally working with a veterinarian trained in rehabilitation to guide you in your pet's recovery.

Type of Surgery: These days, it seems the general default recommendation for all dogs diagnosed with cruciate ligament disease is to have a TPLO surgical procedure done. This is a highly invasive surgery that involves an osteotomy, or cut through the top of the shinbone. The upper segment of the bone is rotated to flatten the slope, and a bone plate and screws are used to lock the bone into its new, leveled position.

While this may be the best surgical option for some dogs, such as giant breeds or highly athletic dogs, it isn't the only surgical approach, and in my experience, the potential risks associated with this surgery are rarely fully explained to clients at the time of their surgical consultation. The complication rate of the TPLO procedure can be as high as 35%, and that risk likely increases if you are not working with a board-certified veterinary surgeon. Complications can range from minor to major concerns, with the following examples:

• Intraoperative hemorrhage

• Incisional problems: infections, seromas

• Inflammation and patellar tendinitis Implant failure: loosening, bending, or breaking of the surgical plate or screws

• Bone fractures: breaks or delayed healing around the surgical cut

• Deep infections requiring intensive medical care

• Meniscal tears

In my opinion, the biggest concern is the risk associated with TPLO surgery and the potential increased risk of developing bone cancer. Some studies have found that dogs that underwent TPLOS were upwards of 40 times more likely to develop bone cancer (osteosarcoma) of the proximal tibia. Again, in my experience, this risk is rarely discussed with pet owners at the time of their surgical consultation.

If surgery is deemed necessary, explore your options. Less-invasive procedures can not only be less expensive but can still produce good-quality results with fewer risks and complications.

Conservative Management:

There is never a need to rush any pet into surgery for a torn cruciate ligament. Conservative management can be explored, and if the results are not satisfactory, surgery can always be elected in the future. Unfortunately, whether they have surgery or not, all dogs with cruciate disease will develop secondary arthritis in the associated knee joint and will also be at risk for meniscal injury in the future. They will also be at increased risk for developing the condition in the opposite knee joint (50-60% of dogs will rupture the cruciate ligament in the opposite leg).

Conservative management can be a particularly good option for elderly pets that may not be good candidates for surgery, pets with concurrent health issues, such as kidney or liver disease, that have increased anesthesia risks, cats, small- to medium-sized dogs, and dogs suspected of having early or partial cruciate ligament tears. The success of conservative management often depends on the extent of the tear and whether the meniscus is also injured.

It is highly advisable to work with a veterinarian trained in rehabilitation therapy to help you formulate a recovery plan for your individual pet. But, in general, conservative management may involve:

• Strict activity restriction: avoid running, jumping, stairs, and slippery floors • Weight control/weight loss • Pain relief • Targeted physical exercises to strengthen the muscles around the joint • Integrative modalities such as laser, acupuncture, PEMF, hydrotherapy, etc. • Custom bracing may be beneficial for some pets • Joint injections, especially for suspected partial ligament tears • Targeted supplements to support joint health, muscle health, and ligament strength • Newer experimental considerations, such as hormone replacement therapy and peptide therapy, may have a role in the future of conservative management of this condition

Prevention/Minimizing Risk:

What can be done to try to prevent cruciate disease?

• Avoid early neutering or consider hormone-sparing sterilization techniques, especially if you have a high-risk breed and/or a large or giant-breed dog. Dogs that are spayed or neutered before 1 year of age have been shown to be at twice the risk for developing cruciate disease.

• If your pet was already neutered under a year of age, consider hormone replacement therapy, especially if you have a high-risk breed.

• Maintain a lean body weight and don't allow your pet to become overweight

• Feed a minimally processed, species-appropriate diet with adequate protein levels

• Walk your dog daily. Controlled walking is the best exercise option for most pets.

• Administer joint and muscle health supplements preventatively, especially as your pet is approaching middle age

• If you have a high-risk breed, consider consulting with a veterinary rehabilitation specialist preventatively to get individualized prevention recommendations and specific exercise suggestions for your pet

• Consider working with a veterinarian trained in Traditional Chinese Veterinary Medicine (TCVM) for pets. They can help identify patterns that may signify an increased risk of ligament issues from a TCVM perspective and recommend corrective therapies to help reduce the risk of injury and support ligament health.