Cranial Cruciate Ligamentous Instability
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The cranial (or anterior in humans) cruciate ligament is one of the major stabilizing structures to the canine knee (stifle).
The ligament is responsible for preventing excessive hyperextension, internal rotation, and cranial (or forward) translation of the tibia in relation to the femur (cranial drawer motion).
Injury to this ligament (partial or complete) results in inflammation in the knee followed by a progressive biochemical process ultimately leading to severe degenerative joint disease (osteoarthritis). It is by far the most common cause of hindlimb lameness in the dog.
Surgical exploration and stabilization of the knee is the preferred treatment with current stabilization consisting of one of three major procedures. Lateral extracapsular stabilizations involve placement of a nylon suture to remove the instability left by a cruciate deficient knee.
This method relies on development of scar tissue to provide knee stability in combination with aggressive rehabilitation.
Most dogs have a good response to extracapsular repairs with better than 80% of patients improving in clinical function according to owner surveys. The TPLO (tibial plateau leveling osteotomy) is an apparently biomechanically superior technique developed within the last 10 years which has excellent anecdotal results and appears to provide improved postoperative range of motion.
An additional technique recently has been advocated in which the tibial tuberosity is advanced (TTA) forward to gain mechanical advantage by changing the pull of the patellar ligament. At present, replacement of the ligament is generally not pursued in veterinary surgery as in humans due to the difference in knee biomechanics.
All dogs with cranial cruciate ligamentous instability are also at risk for damage to the meniscus in the knee which can occur in approximately 50% of cases and can occur post-operatively in a small number of individuals. Primary treatment for meniscal damage is removal of the diseased tissue.
The overall result of this injury is a permanent ligament deficiency to the knee, however, a vast majority of dogs will improve clinically postoperatively over a 3 month period of time to return to an active good quality of life.
 Tibial
Plateau Leveling Osteotomy (TPLO)
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