During his prime, Ginger, an older Labrador retriever, tore both anterior cruciate ligaments (ACLs), one after the other. Also called cranial cruciate ligaments (CLLs), these structures, along with the caudal cruciate ligaments, connect the thigh bones to the shinbones in the hind legs, stabilizing the joints called the “stifles” in four-legged animals. The stifle is analogous to the human knee. This can create confusion among lay people. When a cow, horse, or goat “kneel” down, they bend their legs in such a way that folks think of the “knees” as being up front. But true “knees,” complete with ligaments, kneecaps, and menisci, are in the hind legs.
Sports fans will be familiar with ACL tears — common injuries in athletes like football players, skiers … and large dogs. ACL injury may be strictly a result of trauma, but in dogs it is believed that there is an element of pre-existing ligament degenerative disease that predisposes affected individuals to such tears. Hence dogs who rupture one ACL often eventually tear the other. Other factors that may increase the risk include aging, genetics, age at neutering, and obesity. Labradors, Newfoundlands, golden retrievers, St. Bernards, bichon frisés, and Rottweilers may have an increased incidence.
ACL tears usually present as severe, acute-onset hind-leg lameness, with many dogs being three-legged lame. Your veterinarian may feel swelling in the stifle. Pain during manipulation helps support the diagnosis. Clicking noises may indicate concurrent tears of the meniscal pads. But the most definitive sign of an ACL tear is laxity in the joint, called “anterior drawer motion,” in which the lower bone can be moved farther forward than in a normal, intact knee. Unfortunately, it can be subtle and sometimes, when a dog is awake, impossible to detect. Definitive diagnosis occasionally requires sedation. What about radiographs? Ligaments do not show up on x-rays. Films may show changes such as increased space between femur and tibia, abnormal bone or sesamoid position, joint swelling, or other minor changes, but radiographs often look completely normal.
Statistics on recovery vary depending on what sources you consult. Dogs under 40 pounds may have up to 25 to 85 percent chance of regaining adequate function with just strict confinement, which can take six months or longer. But for big dogs like Ginger, at 80 pounds, there is no controversy. Large dogs have very little chance of healing well without surgery. The longer they walk around on an unstable joint, the more risk of permanent damage. It’s reasonable to try four to six weeks of strict confinement, i.e., short leashed walks only, combined with weight control and anti-inflammatory analgesic medications. “Isn’t it better not to give pain killers, so they don’t run around?” owners sometimes ask. An understandable theory, but studies show that animals (including people) heal better when not in pain. If lameness isn’t improved after this period, it’s time for surgery. There are several different surgical options to stabilize the stifle, each with its own pros and cons. I recommend consulting a board-certified surgeon to choose which technique is best for each specific case.
But Ginger’s story today isn’t actually about his ACLs, at least not directly. Years ago, Ginger had surgery first on one knee, then the other. He recovered well. As he aged, he had some stiffness, pain, and muscle atrophy of his hind end. Then one day recently he became suddenly lethargic, acting “clumsy,” and reluctant to walk. On physical exam, Ginger clearly had pain in his neck. Differential diagnosis included intervertebral disc disease (i.e., “slipped disc” in his neck), spinal cord tumor, infection in the vertebrae and discs called diskospondylitis, even Lyme disease. Poor Ginger. Already chronically weak in his back end, adding the sore neck made moving around a real challenge. We started a cocktail of pain medications, and doxycycline to cover for Lyme, but Ginger continued to deteriorate. Radiographs looked normal. “But many spinal cord lesions require MRI for diagnosis,” I told his family. Here was the dilemma. How much do we put Ginger through, considering his age, general condition, and the expense? I called the specialist to discuss the case. MRI would run around $3,000, but they advised other testing first, including abdominal ultrasound, which might up the bill to four or five grand. Just for diagnostics. “If it’s a slipped disk, it might be surgically correctable,” I informed the owners. I knew another big lab who had similar signs, then neck surgery, and was still going strong. On the other hand, if MRI showed something like an inoperable tumor, we would have an answer, but not a cure. We went back and forth about what to do. Could we skip preliminary testing? I asked the specialist. Go straight to MRI? Sure, but we might miss some other life-threatening disease. How likely was that, I wondered? Back and forth.
Ginger’s family consulted the specialist in person, initially thinking to skip other testing and go straight for the MRI, focusing the expense on the procedure most likely to give a diagnosis for the neck pain, but the doctor persuaded them to proceed with abdominal ultrasound first. Good thing: They found a mass on Ginger’s spleen, possibly malignant cancer. Now even if MRI were to reveal a treatable neck lesion, Ginger would need a splenectomy, in addition to spinal surgery, all with guarded prognosis. As Ginger was a senior citizen already having trouble walking, that just didn’t seem humane. We tried conservative medical treatments, but his condition rapidly declined, and one snowy January weekend, we let him go peacefully at home.
Elderly animals often have multiple problems. It makes sense to be as thorough as possible when making big medical decisions. Had the family opted to trim costs by skipping the ultrasound, we might have put Ginger through expensive and painful procedures only to lose him to cancer unrelated to his neck problem. His knee surgeries had been worth every penny, giving him many years of happy mobility, but this time, the decision not to proceed was the right one.