The most common cause of pelvic or hind limb lameness in the adult dog is anterior cruciate rupture. A recent AVMA study reported owners spent over $1.32 billion to treat ruptured cruciate ligaments in their dogs during a one-year period.

Ruptured cruciate ligaments are seen more often in spayed or neutered dogs. Overweight or obese dogs are more prone to this injury as well. Once the tendon ruptures on one side the opposite side will often rupture soon after. This is because the remaining hind limb has to carry even more weight after the initial injury occurs. Patients with anterior cruciate damage are usually over 5 years of age.

The stifle or knee joint is hinge-like and its design allows for optimal motion between the tibia (Shin) and the femur (Thigh bone). The bones of this joint are not interlocked as are the hip, shoulder, and elbow joints. The tibia and the femur are held together with several strong ligaments and a fibrous joint capsule. Two fibrocartilaginous meniscus are interposed between the two bones to cushion them. There are two cruciate ligaments which run between the bottom of the femur and the top of the tibia. The function of these ligaments is to provide stability between the two bones. The anterior cruciate is the ligament more prone to damage. Once damage occurs, the two bones slide between one another with the tibia moving forward. This motion is known as an anterior drawer sign. Often the medial meniscus will be damaged as the tibia shifts forward.

Most pets with anterior cruciate rupture have a history of acute trauma or of suddenly turning, followed by intense pain and carrying of the affected limb. On examination an anterior drawer sign is diagnostic for a torn anterior cruciate. When a dog is in pain and on its guard it may be necessary to sedate it in order to relax the leg muscles and allow observation of the anterior drawer sign.

Surgical correction is the preferred treatment for full ligament ruptures. In cases where the ligament is simply stretched, rest, weight reduction, and strengthening of the quadriceps through exercise may help. Arthritis is common after injury. Anterior cruciate injury is the most common cause of arthritis in the stifle or knee joint.


References

Wilke, VL, Robinson DA, Evans, RB: “Estimate of the Annual Economic Impact of Treatment of Cranial Cruciate Ligament Injuries. JAVMA 2005; 227: pp. 1604-1607.