Cranial cruciate ligament rupture is one of the most common causes of hindlimb lameness in the dog and the major cause of degenerative joint disease (arthritis) in the stifle joint.

Function of the CrCL ligament: The cranial cruciate ligament provides stability to the knee (stifle) joint by controlling internal rotation and cranial (forward) translation of the tibia during weight bearing. A complete or partial tear of the cranial cruciate ligament causes instability in the joint which is why your pet doesn’t want to bear full weight on the limb. This tear in the ligament creates inflammation, increased joint fluid (effusion), and arthritis formation in the joint. In addition to the torn cranial cruciate ligament, the meniscus can also be damaged. The meniscus is a cartilage cushion between the femur and the tibia. Surgical intervention will benefit your pet’s knee by allowing the damaged tissue to be removed and returning stability to the joint.

Cause:
Cruciate ligament ruptures in dogs are usually not due to traumatic events as is the case in humans, but
are due to degenerative process that slowly weaken the ligament until ultimate failure. Obesity, steroid
use, or endocrinopathies can hasten failure of the ligament.

Clinical Signs:
Many dogs are middleaged or older when the rupture occurs, however, we are seeing increasing numbers of younger dogs (1 to 4 years old). Breeds commonly affected include Labrador Retrievers, Pit Bulls, Rottweilers, Akitas, Border collies, Huskies, German Shepherds, and Mastiffs. Many small breed dogs and some cats also develop cruciate ligament tears.

Common signs include:

• stiffness on the limb after rest;
• varying degrees of weight-bearing lameness;
• not bearing weight on the limb;
• if the meniscus is torn sometimes a clicking noise is heard from the stifle when the pet walks on the
limb or when the stifle is flexed
• dogs with bilateral disease may have difficulty getting up and walking

Diagnosis:
Cranial cruciate ligament injuries can be diagnosed by reproducing the instability with the tibial compression test or the cranial drawer test (drawer sign). If the meniscus is damaged, a click may be audible or palpable. The stifle is thickened. Radiographs reveal effusion (fluid) within the stifle joint and signs of osteoarthritis, and these radiographic signs may be evident even before the tear in the cruciate ligament is obvious on physical examination. About 40% of dogs will tear the cruciate ligament in the opposite limb within 1 to 2 years; some already have a cruciate ligament tear in the opposite stifle at the time of diagnosis.

Treatment:
There are many surgical options to treat cranial cruciate ligament injuries in dogs and cats. These include extracapsular fixation (fishing line technique), the tightrope procedure, TPLO (tibial plateau leveling osteotomy, or the TTA (tibial tuberosity advancement).

The surgeons at Animal Specialty & Emergency Hospital can discuss these procedures with you and recommend the best option for your pet. For most large breed, active dogs we recommend the TPLO procedure. The TPLO is the only procedure that has been shown to reduce the progression of arthritis. The surgeons at Animal Specialty and Emergency Hospital have an excellent track record of returning dogs to athletic or working activities following TPLO surgery.

Following surgery, the staff at ASEH recommend physical rehabilitation sessions with Carrie and Dr. Lawrence. Physical rehabilitation improves the recovery of pets from surgical conditions and injury by the use of physical modalities in conjunction with therapeutic exercises, analogous to “physical therapy” in humans. At ASEH, we customize a rehabilitation protocol for each patient, utilizing a combination of cold laser, neuromuscular stimulation (NMES), cavaletti poles, therabands, stability balls, manual techniques (stretching, passive range of motion exercises), and proprioceptive training. We also provide owners with at-home exercises to perform between clinic visits.

Tibial Plateau Leveling Osteotomy
The TPLO surgery is a very successful treatment for cranial cruciate ligament rupture. The Surgeons at ASEH have performed hundreds of these surgeries with excellent clinical results. Preoperative X-rays are taken and the slope of the tibial plateau is measured. At surgery, stifle joint exploration is performed to assess the medial and lateral meniscus cartilages (that sit between the femur and tibia), and if a damaged meniscus is identified the damaged portion is removed. A curved cut in the bone (an osteotomy) is performed in the top of the tibia, and the bone segment is rotated to flatten the slope of the tibial plateau, and prevent cranial tibial thrust (it is the cranial tibial thrust that occurs when your pet weight-bears that causes the lameness and instability associated with CrCL disease). The bones are held in place with a bone and screws while the bone heals (typically 8 to 10 weeks).

	Above and Right: Preoperative x-rays of a dog with a ruptured cranial cruciate ligament.
	Above: Postoperative x-rays of a TLPO. The bone segment has been rotated and fixed in place with a bone plate and screws, making the stifle more stable when the pet is weight-bearing Above: The bone has healed

Extracapsular Stabilization, TightRope CCL Technique

This technique is an extracapsular stabilization technique that utilizes bone tunnels allowing bone-tobone fixation. The TightRope is FiberTape (Arthrex Vet Systems), which is stronger than the monofilament nylon that is commonly used with other extracapsular techniques. The TightRope procedure is a less expensive alternative to the TPLO technique for medium to large sized dogs, and recently instrumentation has become available allowing this technique to be used in small dogs and cats. The TightRope technique is not recommended for patients which may have compromised connective tissue healing.

Extracapsular Stabilization, monofilament nylon

At Animal Specialty and Emergency Hospital, we generally reserve this technique for smaller dogs and cats. The extracapsular technique is not recommended for patients which may have compromised connective tissue healing.

Cranial Cruciate Ligament Disease in cats

Cats can rupture either the cranial or the caudal cruciate ligaments. Typically the cause is trauma. Cats present with a non-weight bearing or a weight bearing lameness that will improve over time, but not resolve. While their small size means they will often function without surgical stabilization of the stifle, generally they will nave a faster recovery and a better return to function if surgery is performed.