What do Tom Brady's, Tiger Wood's, and Fido's knees have in common?

My previous two blog posts (Part 1, Part 2) describe vexatious tears of the anterior cruciate ligaments in athletes, but humans are not alone in sustaining injuries to this critical knee ligament.

The knees of dogs, horses, cattle, and other quadrupeds are called stifles. To add to terminology confusion, our ACL is their cranial cruciate ligament. Regardless of the name, the CCL can tear in quadrupeds just as the ACL can in bipedal humans. We don’t think about cattle running and jumping much, but bulls risk the integrity of their CCLs when servicing cows, and cows in heat risk theirs the same way when riding other cattle. A bovine slipping sideways while standing on its hind legs immensely stresses its stifle, which can cause the CCL to tear. (Gary Larson’s cattle and deer are always standing up. No telling how many of them have CCL injuries.)

A CCL tear is the most common cause of lameness in dogs and, left unattended, results in the joint not tracking properly, thereby grinding the cartilage off the bone surfaces and leading to osteoarthritis. Large breeds are particularly susceptible, as are overweight and older dogs of any size. In younger ones, an acute injury from suddenly changing direction or jumping down from an elevation can be causative, which puts agility and disc competitors at particular risk.

For older canines, CCL tears more often result from accumulated degeneration. Dogs of any age are susceptible to the “weekend warrior syndrome,” where their muscles and ligaments become deconditioned while their owners are working and then overstressed when their owners finally have time to play.

A tear causes the dog to avoid weight bearing on that leg. Nonoperative management depends on the owner’s preference and the pet’s age, activity level, and general health.

In general, dogs undergoing surgical correction and followed by weight loss if necessary, nonsteroidal anti-inflammatory medications, and a specific rehabilitation protocol do better. Compared to humans, however, dogs are disinclined to use crutches or perform hamstring and core strengthening exercises, so the surgery must provide a limb that is immediately stable for weight bearing. Hence, there are work arounds to substitute for the function of the CCL rather than replacing it.

Barclay Slocum, a veterinarian in Oregon, developed the tibial plateau leveling osteotomy (osteo = bone, otomy = cut). The TPLO rotates the tibia’s joint surface so that it is nearly perpendicular to the bone’s shaft. This shift prevents the femur from sliding forward on the tibia, which provides the same function as an intact CCL. Slocum fixed the cut in the bone securely with a steel plate and screws.

This allowed the dog to begin weight bearing immediately, which minimized deconditioning of all its muscles and ligaments. When Slocum saw that his technically demanding procedure was successful, he did something unusual in veterinary and medical practice. He patented the procedure, and his reports at meetings and in journal publications were short on technical details. Rather he taught the procedure out of his veterinary practice and required signed contracts from his learners that they would not teach the surgical details to others. This approach did not sit well with many veterinarians, but Slocum had a point. Whereas he was achieving excellent results, inexperienced and headstrong surgeons might struggle with the operation, not attend to details, have unsatisfactory outcomes, and give the TPLO a bad name.

An alternative procedure to the TPLO is the tibial tubercle advancement procedure. If you feel your kneecap and begin sliding your fingers toward your ankle, you first encounter the tough, springy patellar ligament and then an inch farther on the hard prominence where it attaches. That bump on the shin bone is your tibial tuberosity, and the TTA moves it forward, which changes the quadriceps’ direction of pull and prevents the tibia from sliding forward on the femur, even in face of a deficient CCL. (The three Swiss orthopedic veterinarians who developed the procedure may have done so in response to Slocum’s closely held TPLO.)

The TTA moves the tibial tubercle away from the tibia except at the bottom edge, where the tubercle is hinged forward and a titanium wedge and fixation hardware secure its new position. As with the TPLO, the TTA allows for some early, limited weight bearing.

Neither the TPLO nor the TTA has distinct outcome advantages over the other, and the choice of procedure may depend on the veterinarian’s personal experience. Both procedures benefit from a graded post-operative rehabilitation program, which can include underwater walking on a treadmill. There are some endearing videoclips on YouTube of contented pooches striding along chest deep in a tub of water. Who supervises such therapy? Either a vet, nurse, or technician who is certified in canine rehabilitation.

******************