Why Is My Pet Limping?

Cranial cruciate ligament injuries in dogs

By Matthew Nicholson, DVM

There are many reasons why a pet may develop a lameness or limp. Some of the causes can be sudden in onset, while many may have a gradual progression. It is important to recognize the onset of symptoms, activities that exacerbate the lameness, duration of signs, and response to any medications. You should be aware that you must not administer any medication to your pet without the direct consent of your veterinarian. Your pet’s tolerance to medication is much different than ours, and there are many human medications that can be toxic to animals due to differences in metabolism.

One of the most common causes for lameness diagnosed in dogs is an injury to the cranial cruciate ligament (CCL) of the stifle (knee joint) in the hindlimb. This ligament is synonymous to the anterior cruciate ligament (ACL) in people. Although the injury can occur from a single traumatic incident, most occur as a gradual weakening of the ligament over time. The reasons for this are numerous, and continue to receive the greatest attention in research.

We have learned that there are structural factors of the knee that may lead to instability and subsequent injury. One factor is the tibial plateau angle (TPA), the portion of the shin bone that makes up the base of knee joint. If this angle is too steep, it may predispose a dog to tearing the CCL due to a shear force. Other factors that may contribute to CCL tear include weakening of the other stabilizers of the knee joint including: the surrounding ligaments, joint capsule, contours of the joint surface (including the kneecap), meniscal cartilages that help to cushion the knee, as well as the supporting muscle groups—in particular the quadriceps and hamstring muscles.

With instability due to a CCL injury, the body responds by trying to stabilize the knee with the development of scar tissue. Our goals in treating a non-surgical case would include redevelopment of muscle tone and mass and trying to control inflammation and pain.

Unfortunately, it can take weeks to months for a dog to recover from a CCL injury without surgery, and many of these patients go on to develop significant arthritis compared to those that have had surgery. For this reason, surgery is often recommended. The goal with surgery is to aid in stabilizing the knee and/or correcting other contributing factors like a kneecap dislocation.

There are several types of surgeries to aid in stabilizing the knee due to CCL tear. Historically, the surgical goal was to re-establish the stability that the ligament used to provide—such as replacement with a graft of the patient’s own tissue, or more commonly stabilization with suture material. Other, newer procedures like tibial plateau leveling osteotomy (TPLO), and tibial tuberosity transposition (TTA), are aimed at reducing the shear force that may have contributed to the tear and stabilizing the knee during weight bearing.

Recovery from surgery typically requires three months. Surgical success rates are generally 90–95 percent when considering the TPLO and TTA procedures. Essentially, this means depending on the procedure, and other factors that may have contributed to the injury, 85–95 percent of patients will have good to excellent use of the injured leg after recovery. Rehabilitation is critical in your pet’s overall success and recovery. This helps address some of the other factors such as muscle tone and muscle memory in stabilizing the knee. It also aids in reestablishing range of motion and comfort.

Matthew Nicholson, DVM, is veterinary surgeon practicing with Veterinary Surgical Centers in Winchester, Va. Contact him at 540-450-0177 or visit veterinarysurgicalcenters.com.