Geoffrey N. Clark, DVM, DACVS

Cranial cruciate ligament (CrCL) injury is a common cause of hind limb lameness and osteoarthritis in dogs. Many studies have reported on surgical techniques to treat this condition, and have compared the results following surgery, but the clinical focus has not been directed on the variable manner in which dogs will present with cranial cruciate injuries. In this study, the clinical characteristics of 150 consecutive cases of canine cranial cruciate ligament injury were evaluated.

All dogs were initially diagnosed by their primary care veterinarian and referred to the author for surgical treatment of their injury. Patients were referred from one of 45 veterinary hospitals in a three state region (NH, MA, ME) during 2012. Preoperative evaluation included orthopedic examination, review of medical history, and evaluation of radiographs, with particular attention to the duration of the injury. Clinical and radiographic signs of an acute or chronic knee injury were noted. Examination findings suggestive of a partial ligament injury were also recorded. Dogs in this study ranged in age from 1 ½ years to 13 years of age and ranged in size from 9 lbs (4 kg) to 141 lbs (64 kg). There were 76 males (3 intact) and 74 female dogs (1 intact). The most common breed presented was the Labrador retriever. There were 38 purebred Labrador retrievers and another 12 dogs considered to be a Labrador retriever mix. There were also 12 Golden retrievers in this study and no other breed was represented by more than 6 dogs. Notable by their relative absence were Rottweilers (3) and Newfoundlands (1).

Surgery was performed in all 150 dogs. An extracapsular stabilization (ECS) or a tibial plateau leveling osteotomy (TPLO) was performed, with the technique chosen based on patient factors (age, size, activity level, tibial plateau angle) and owner preference. An arthrotomy was performed in each patient and intra-articular findings were noted. A complete ligament injury was noted in 122 dogs (81.3%) and a partial tear was noted in 28 dogs (18.7%). The medial meniscus was torn in 73 dogs (48.7%). Four dogs in the study required a second surgery on their opposite knee during the study period. Elapsed time between the two surgeries for these dogs ranged from 1 month to 3 ½ months. Another 28 dogs in the study group had previous surgery for a cranial cruciate ligament injury in the opposite limb. Elapsed time between knee surgeries for these dogs ranged from 3 to 42 months, with a mean of 17.9 months.

It is clear from the information in this report, and supported by many earlier reports, that cranial cruciate ligament injury in the dog has multiple forms depending on degree of injury and degree of chronicity. Patient outcome following CrCL surgery, regardless of technique employed, will be greatly influenced by factors such as duration of injury, complete or partial ligament injury, and presence of an intact or damaged medial meniscus. Our clinical reports and comparison of outcomes with various techniques should reflect these differences.