Dog and cat knees are similar to humans. For example, knees have five ligaments, two menisci, a knee cap, and joint cartilage. The ligament most commonly affected in dog and cat knees is the cranial cruciate ligament or sometimes referred to as anterior cruciate ligament. It is the same ligament most commonly damaged in professional athletes.
Dogs and cats usually tear this ligament when out running around, or sometimes when landing wrong after a jump. Evidence show that the torn ligament in most cases is already diseased or weak, and an apparent traumatic incident is only the last straw. Occasionally No apparent trauma would be detected and the symptoms may appear gradually over a period. The reason for this weakness has not fully explained and demand much research and attention.
The cranial cruciate ligament is a large, strong ligament located within the knee joint. It is not actually a single structure, but is, in fact, made up of a bundle of individual fibres tightly bound together to form the ligament. Most of the time when the ligament is injured, it is completely torn in half. Sometimes, though, only a portion of the ligament will tear. Though only a portion of the ligament may be torn, the whole ligament is damaged.
When a cranial cruciate ligament is torn, it causes sudden pain and often results in the pet holding its leg up. It also causes instability in the knee joint. The pet may put the leg down and start using it within a day or so, but will continue to limp for several weeks. Normally, at the end of several weeks, the initial pain subsides and the pet is willing to use its leg more; however, the joint remains unstable. Every time the animal puts weight on the leg, the tibia (shin bone) slides forward in relationship to the femur (thigh bone). This abnormal motion causes wear and tear on the joint cartilage, causing pain and leading to arthritis. This motion can also put excessive stress on the menisci (C shaped pieces of cartilage within the knee joint), causing damage or tearing.
Conservative management usually fail to yield good recovery in most dogs but some small dogs may do just fine providing the right care is given, such as anti-inflammatory medication, hydrotherapy, Acupuncture, physiotherapy, weight control and diet modification. There are many other treatment modalities, such as joint supplements, Acupuncture and other natural remedies. Although some show some subjective improvement no hard evidence had been produce to show consistent results.
Surgery is the only corrective measure for cranial cruciate ligament injuries. Many surgical procedures have been tried on people and animals during the last 60 years; however, most orthopaedic surgeons agree that the procedures are not as successful as they would like. Knees that suffer this injury are never completely normal even after surgery is performed. Surgery does, though, stabilize the knee, allowing it to regain normal motion and thereby reducing the formation of arthritis. Surgery has been and remains the treatment of choice for this injury. If surgery is not performed, progressive arthritis will occur and the lameness will worsen with time. In the next session I will discuss the rational behind choosing the right treatment for the specific dog. This is a complex issue and require some understanding of cruciate disease and therefore separate attention.