Cranial cruciate ligament injury is a common cause of limping in dogs. Although it is prevalent in larger dogs such as Newfoundlands, rottweilers, Labradors, and Staffordshire terriers, small dogs can develop this injury as well.
The cranial cruciate ligament or CCL is analogous to the anterior cruciate ligament or ACL in humans. It runs from the femur (thigh bone) to the tibia (shin bone), and one of its main functions is to prevent movement between those two bones when walking. Instability occurs when the ligament is torn, which leads to inflammation, discomfort, and eventually arthritis.
Whereas ACL tears in people are usually the result of an athletic or traumatic injury, CCL tears in dogs are more commonly a degenerative condition. Over time, wear and tear to the ligament causes small ruptures in the fibers that make up the ligament, which can eventually tear completely. Frequently, what seems like a sudden injury is simply the last bit of the ligament tearing.
Dogs with CCL tears may limp on and off for weeks to months. The degree of lameness can range from mild, intermittent stiffness to complete unwillingness to use the leg. The limping is usually worse after exercise and can become more pronounced as the injury worsens. Dogs may also have difficulty rising or may sit with their legs extended out to the side in a “lazy sit” position. Dogs will rarely cry out in pain, but if they are limping, they are likely very uncomfortable.
Diagnosis of CCL tears is usually based on a physical exam, where veterinarians look for joint swelling at the knee, thickening of the knee from scar tissue, and instability. Affected dogs also experience pain with full extension of their knees. X-rays are typically the next step; while the ligament itself is not visible on x-rays, joint swelling and arthritic changes can be seen. The purpose of X-rays is to rule out other things such as bone or joint tumors, infections, or fractures.
Treatment of CCL tears may or may not involve surgery. Nonsurgical treatment is usually reserved for mild cases of partial tears or in small dogs. The goal is to encourage scar tissue growth that is tight enough to hold the femur and tibia stable during walking. Bed rest for 8 weeks is very important for the scar tissue to correctly build up. Any weight that the leg bears during this time will cause stretching of that scar tissue, rendering it much less effective. As such, this method is much more successful in small dogs weighing less than 10 pounds to 15 pounds. There are many braces on the market that claim to stabilize knees with CCL tears, but studies have thus far failed to show any benefit. Additionally, many dogs refuse to use their legs when wearing a brace, and sores can develop from ill-fitting braces, so they should be used with caution.
Surgery is usually recommended for active dogs of any size, particularly larger dogs. The “tibial plateau leveling osteotomy” is one of the most commonly recommended surgeries. This procedure rotates the top part of the tibia to prevent sliding of the femur when the dog is walking. Studies have shown that by 12 months after surgery, dogs undergoing TPLOs bear weight similarly to dogs with intact cruciate ligaments.
A situation in which surgery is typically necessary is when a meniscal tear occurs along with a CCL tear. The menisci are discs of cartilage sitting between the femur and tibia that can get caught between the two bones, leading to tearing. Dogs with meniscal tears typically experience much more pain and limp significantly more than dogs with CCL tears alone. Injuries involving a meniscal tear do not respond well to strict rest and usually require surgery.
There are many variations of surgical and nonsurgical procedures that are currently being performed to treat CCL disease, and not one has been definitively proven to be superior in all dogs. Every patient is slightly different and each treatment option comes with a unique set of risks, so it is important to have a conversation with your veterinarian before choosing one.
Christine Hsueh, DVM, DACVS-SA, is a boarded surgeon who works out of the SAGE Campbell hospital. She chose surgery as her specialty because she loves to work with her hands and fix things, especially when it comes to four-legged friends because she knows how important pets are to their pet-parents and vice versa. Her specific areas of interest are minimally invasive surgery including arthroscopy, laparoscopy, and thoracoscopy; microvascular and ureteral surgery; canine cruciate disease; fracture healing and advanced fracture repair techniques; neurologic surgery. Learn more at SAGECenters.