What Is It?
Your dog’s knees, just like your own, are supported and stabilized by several ligaments (fibrous structures that attach bone to bone). The cranial cruciate ligament of dogs is analogous to the anterior cruciate ligament, commonly referred to as the ACL, of humans. This ligament keeps the tibia from sliding too far forward and limits internal rotation of the knee. Dogs or cats who are suffering from acute damage to the cranial cruciate ligament typically present to our hospital with non- or partially weight-bearing lameness of the affected hind leg.
In many cases, a thorough orthopedic examination will raise suspicion of a cruciate ligament injury. Most pets are painful upon palpation of the affected knee, and your veterinarian may identify swelling in the area or a soft “click” that typically represents secondary damage to the associated meniscus (a cushioning structure of the knee). Chronic cases of cruciate ligament disease may also exhibit evidence of degenerative joint disease (stiffness, creaking or crunching of the joint referred to as crepitus) or thickening of other fibrous structures associated with the knee (“medial buttress”). In either case, your doctor will evaluate for presence of a “cranial drawer” or “tibial thrust” – two actions of the knee that suggest that the function of the cruciate ligament has been compromised. Radiographs (x-rays) of the area will help to rule-out other potential causes of lameness as well as to characterize the extent of secondary changes. While x-rays cannot identify the cruciate ligaments specifically, there are several classic signs on x-rays the are supportive of cruciate ligament disease.
Management of cruciate ligament injuries may involve surgical or medical treatment. For most cases, surgical management provides the best stabilization of the joint and the best long-term prognosis. Both options are discussed below:
Unfortunately, there is no current surgical repair method that can restore a cruciate ligament after it has been damaged. Instead, surgical corrections are aimed at stabilizing the knee in other ways. These techniques include:
a. Extracapsular Repair: This technique is often elected for small dogs and cats as it is unlikely to provide adequate support for larger patients. The surgical repair procedure involves the placement of a thick monofilament suture or surgical cable outside of the joint to mimic the function of the cruciate ligament. It provides stabilization, but degenerative joint disease (arthritis) is still likely to develop. Rarely, this surgical repair can fail if the suture or cable subsequently breaks.
b. Tibioplasty: Large dogs typically do better with a more substantial surgical procedure. Doctor preferences vary, but the Tibial Plateau Leveling Osteotomy (TPLO) and Tibial Tuberosity Advancement (TTA) procedures are most often recommended. Both options involve surgical adjustment of the proximal tibia in an attempt to minimize sliding forces. These procedures are best performed by a board-certified veterinary surgeon. These types of surgeries provide the best stabilization of the joint, though degenerative joint disease (arthritis) can still develop. These surgeries rarely fail, but there is a small percentage of patients that do not recover as well as expected.
Given adequate time and rest, many dogs can develop sufficient stifle stabilization without surgical intervention. Again, our goals are not to promote specific healing of the cruciate ligament, but to allow other soft tissue structures in and around the knee to “scar” down and provide additional support. This process typically takes 4-8 weeks, during which patients should be strictly limited with regard to their exercise habits. Short, leashed walks to urinate and defecate are acceptable, but avoid any running, jumping, or playing. It is best to confine patients to a small room or crate/kennel when unsupervised to avoid injury during an owner’s absence. Non-steroidal anti-inflammatory medications and other pain-relieving medications are used during this period to maintain patient comfort and support healing. Medical management does not provide the same degree of stabilization as surgical repair, so most patients will develop significant degenerative joint disease (arthritis) if medical management is chosen alone.
Cranial cruciate ligament injuries can be the result of traumatic injury to the affected leg or can be related to chronic degenerative disease in certain breeds. These injuries may also occur secondary to other orthopedic conditions of the knees, including medial patellar luxation (kneecaps that “pop” in and out of place) or inflammatory or infectious joint disease. Maintaining your pet at an optimal weight and promoting regular exercise are two important factors in preventing orthopedic disease. Your veterinarian can help identify other risk factors for your individual pet. Unfortunately, most dogs develop bilateral cruciate disease, so any possible preventative steps should be pursued to prevent disease in the opposite leg.
Written by Kevin Roeser, DVM
Content prepared by St. Francis Animal Hospital, 1227 Larpenteur Ave. West, Roseville MN. 55113