Ligaments are strong, dense tissues in the skeletal system that connect the ends of two bones across a joint. Their function is to stabilize a joint. The most common knee injury in dogs is rupture of the Cranial Cruciate Ligament (CCL), also frequently referred to as the Anterior Cruciate Ligament (ACL). According to Vet Surgery Central, more than 600,000 dogs in the U.S. have surgery a ruptured CCL every year. The CCL plays a critical role in stabilizing the stifle of a dog (known as the knee in humans) against front-to-back forces. It prevents the tibia from shifting in front of the femur, controls excessive internal rotation of the joint and hyperextension, and is the structure most commonly injured.
Accordingly to Veterinary Partner, this is the procedure for a TPLO Surgery. "Before surgery, an x-ray of the stifle is taken to measure the angle at the top of the shin bone, called the tibial plateau angle. The goal of the surgery is to reduce this angle so that dynamic joint instability (cranial tibial thrust) is eliminated. This is usually accomplished by creating a post-surgical angle of between 4 and 10 degrees, an angle not much different than is found in the human knee. In most cases the surgical procedure starts with an exploration of the inside of the stifle joint. This can be done arthroscopically or with open joint surgery. The purpose is to assess the meniscal cartilages for any possible damage. Damaged cartilage must be removed if the dog is to regain normal pain-free function. The TPLO procedure itself involves the use of a curved saw blade to make a curved cut on the inside, or medial, surface of the top of the tibia. The cut top portion is then rotated to create the desired tibial plateau angle. A stainless steel bone plate is then placed on the bone to hold the two pieces in their new alignment.