Cranial Cruciate Ligament Injuries

Cranial cruciate ligament (CCL) injury, the equivalent of the anterior cruciate ligament (ACL) injury in humans, is the most common orthopedic problem in dogs. In 2006 an article printed in the The Wall Street Journal reported the “number of dog knees undergoing cruciate-ligament repair each year in America at more than 1.2 million – approximately five times the number of human procedures, although humans outnumber dogs in the U.S. by nearly five to one”.

What do you do if your dog needs surgery…

I asked Fred Pike, DVM, DACVS from Veterinary Specialty Hospital in San Diego, California to answer a few questions about surgical management of the canine cranial cruciate ligament injury.

AD:What are the current surgical options available?

FP: Common surgical options include tibial plateau leveling osteotomy, tibial cranial closing wedge osteotomy, tibial tuberosity advancement, lateral suture, and the tightrope technique.

AD: How do you decide which procedure to use?

FP:Several factors are considered when recommending a specific surgical procedure for a patient including patient age, preoperative activity level, family lifestyle, breed, tibial plateau angle, tibial geometry (anatomy) and body weight / body condition score. One of the most important intraoperative findings that influence the recommendation for a given procedure is the integrity of the meniscus.

AD:Do you see a pattern with certain breeds that do better with one procedure over another?

FP: Personal experience suggests that certain breeds do better with certain procedures. For example, in my experience, a TPLO is the surgical treatment of choice for Rottweiler and terrier breeds appear to recover faster with the TTA technique. It is important to note that this statement is a personal opinion and controlled studies are not currently available to support superior outcomes with one procedure over another within a given breed.

AD: What are realistic expectation for returning to sporting activities after surgery?

FP: The prognosis for return to activity is dependent upon factors including preexisting arthritis, partial versus complete CCL rupture, concurrent meniscal pathology and the surgical procedure performed. With appropriate surgical intervention and postoperative physical therapy, a return to sporting activity should not be considered an unrealistic goal.

AD: Do cranial cruciate ruptures accounts for 25-30% of stifle lameness?

FP: The percent of lameness is dependent upon the breed and size of the dog. I would agree that CCLR accounts for approximately 25% of stifle lameness in small breed dogs but the percentage is closer to 90% in large breed dogs.

AD: Can these injuries be acute (caused by an athletic or a traumatic event – 20% of cases) or chronic (degenerative)?

FP: Traumatic tears are very rare and are generally only seen in competitive or working dogs. In several cases of acute tears (thought to be traumatic), histopathology frequently supports a degenerative (chronic) process.

AD: Are females are affected more than males, but all dogs are susceptible to them. Can a ligament can usually stand up to 4 times the dog’s weight before breaking.

FP: In 20% of the acute rupture cases, the cause is exceeding the strength of the ligament. The literature is conflicting on the influence of sex as a risk factor for CCLR with recent studies not supporting sex as a risk factor. With respect to traumatic tears, the load / force placed on the ligament is only part of the etiology for ligament failure. Other factors include torque, degree of preexisting collagen degeneration, trochlear notch size, etc.

AD: Is it true that ruptures left untreated show degenerative changes within a few weeks and severe changes within a few months.

FP: This is true and well documented in several studies; however, the rate of progression of degenerative change is related to the severity of the rupture.

AD: Will medial meniscal damage from abnormal joint mechanics occurs in about half the cases.

FP:  X-rays are rarely diagnostic — diagnosis usually requires an MRI to see ligament and meniscal pathology and possibly an arthrocentesis (pulling fluid from the joint – joint cytology) to rule out sepsis and immune-mediated disease. The percent of medial meniscal damage is dependent upon the method used to evaluate pathology (MRI, arthroscopy, visualization, probing). The best method of evaluating meniscal pathology is with probing AND arthroscopic evaluation. MRI may be considered in patients where CCLI is suspected but stifle instability is not present. The small size of the canine CCL (relative to the size of the human ACL) is the limiting factor for the diagnosis of CCLI using MRI.

AD: Is is true that conservative therapy (rest) can be used for dogs under 33 lb, but surgery is recommended for larger/heavier dogs because it speeds recovery, prevents degenerative changes, and improves function.

FP: It is important to note that with conservative therapy, the ligament does not heal; stifle support is provided by periarticular fibrosis (scar tissue) that minimizes cranial translation of the tibia thereby decreasing stifle effusion and pain. A body weight of less than 40 lbs has been reported to be associated with a positive outcome without surgery; however, no controlled studies have been preformed to support this subjective assessment. In my opinion patient age, activity level, desired function, degree of instability, and meniscal status are far more important factors than body weight in determining the need (and benefit) of surgical intervention.

AD: Regardless of surgical procedure, is the success rate is about 85%, with 10%- 15% of cases requiring a second surgery because of subsequent meniscal damage.

FP: The subsequent meniscal tear rate ranges from 2-22% depending upon the procedure. The TPLO has been shown to have a “protective effect” on the meniscus and in my experience is the preferred technique for patients with CCLI that do not have meniscal injuries at the time of the initial surgery.

AD: Will 40% of the cases, the second knee will rupture in within 18 months?

FP: In Labradors, the literature states that 50% of patients will tear the contralateral CCL within one year. The risk is not published for other breeds.

AD: Is it reasonable to say that in general, dogs with CrCL injuries should not be bred.

FP: A genetic component is suspected to be involved with the collagen degeneration that contributes to CCL failure and supports the recommendation that affected dogs should not be bred. This genetic component has been documented in Newfoundland dogs but to my knowledge has not been confirmed in other breeds.