Canine Stifle Disorders, Including Patellar Luxation

Dogs commonly develop problems with their stifles (knees) that may be due to inherited factors, injuries or both. The most common problems we see are medial or lateral luxating patellas (loose kneecaps) and torn anterior cruciate ligaments. Ligament tears are very common in large breed, activedogs, especially Labradors. Luxating patella problems are more common in small breed dogs. Any dog, however, can have either condition.

Medial or lateral luxating patella is a multi-factorial problem that can be inherited and due to conformation abnormalities, but it is often caused by traumatic injury, jumps, falls and/or uncontrolled weight gain. The patella may sit in a shallow groove, the leg may have slight rotation and/or the hip may not be quite aligned perfectly. This will allow the kneecap to displace to the side,outside of the patellar groove. If it displaces towards the inner side of the leg, it is a medial luxating patella, and if it deviates to the outer side of the leg, it is a lateral luxation. This condition can be non-painful in mild cases or it can become very painful and debilitating in severe cases. It is graded from 1-4. Grade 1 and some grade 2 luxations may never need any therapy or surgery, depending on the dog and the amount of activity they engage in. In general, the patella remains inside of the groove and rarely pops out. Grade 3 and 4 luxations involve the patella going out of the groove a fair amount of the time and almost always requires treatment, including surgical correction. Luxating patellas often leads to arthritis and limb dysfunction as the pet ages, so pain control and weight control is a must. The diagnosis is made by palpating the knee and determining if it can be displaced from its normal resting place. Often, x-rays are taken to determine degree of severity. 
 
Anterior cruciate ligament tears can occur in one or both rear legs. It causes a sudden lameness in the case of a complete rupture, but may be a mild, intermittent lameness in the case of a partial tear. Diagnosis is by palpating the knee and finding an “anterior drawer sign”, where the knee can be displaced forward. Treatment usually involves surgery to stabilize the knee and prevent significant arthritis. Surgery usually allows return to normal activity for most dogs, but it is costly.

Knee injuries are very common and the need for surgery depends on many factors. All patients exhibiting lameness need to be put on appropriate pain medication, put on weight loss diets if overweight, and rested for several weeks to decrease inflammation associated with the injury.