Patellar Luxation in Dogs
In simpler terms, “patellar luxation” means the dislocation of the kneecap. It is also sometimes referred to as floating kneecaps. This condition occurs when the kneecap, or the patella, is dislocated from its normal position in the groove of the femur.
When the kneecap dislocates, it cannot return to its normal position until the quadriceps (or thigh) muscle relaxes and increases in length. Therefore, it will sometimes “lock up” with the foot held off the ground. An affected dog will often have hopping or skipping on the leg, which is typically the first sign an owner will notice that something is wrong. Some dogs will have the kneecap spontaneously pop back into the groove, and they go on walking normally again. In more severe cases there may be prolonged dislocation and lameness in that leg. At the moment the patella pops out of the groove, the dog may feel pain, causing him to yelp or lick and bite at the knee area. After the kneecap is out of position, however, the dog will rarely feel pain any longer. If your dog continues to carry a hind leg, as mentioned above, you need to seek veterinary assistance. Prolonged floating of the kneecap outside of its normal position can cause permanent damage to the cartilage of both the kneecap and the femur.
Your veterinarian will most likely begin with an examination to feel for movement in the kneecap. This can sometimes require a small amount of sedation so the dog will relax enough to make a thorough observation. Top and side view x-rays may also be needed to detect bending or twisting of the femur and tibia bones. The bending can predispose dogs to this condition, and in severe cases may require surgical correction.
The severity of a luxating patella is expressed in terms of “grades”. There are 4 grades: 1 being the least severe, and 4 being the most severe. If grade 1 is diagnosed, the kneecap is returning to its normal position spontaneously. In this case, most veterinarians do not treat the luxation. Occasionally, they may try to stabilize the leg and knee in a sling while the patella is in the femoral groove. This sling is left on for around two weeks and the dog’s mobilization is limited to see if the patella will stay in place. Unfortunately, this technique is not always successful. Surgery is typically recommended for grades 2-4. There are several different surgical techniques that may be used. Some dogs require one or all of the techniques. The type of procedure will be determined on an individual basis depending on the severity of the condition and the veterinary surgeon that has examined your pet.
Follow-up treatment after a successful procedure will include slow leash-walks for a minimum of 4-6 weeks (avoid running and jumping), and yearly exams to check for progress.
There are two ways that the kneecap can luxate: to the inside of the knee (medial luxation) and to the outside of the knee (lateral luxation). Medial patellar luxation is most common in (but certainly not limited to) toy and miniature dog breeds. It is most prevalent in Yorkies, Pomeranians, Pekingese, Chihuahuas, and Boston Terriers. Lateral patellar luxation is quite rare, and is usually seen in larger breed dogs. Female dogs are more likely to acquire the condition, but it occurs in males commonly as well. Affected dogs often have genetic malformations in the femoral groove that the patella normally lies in. The groove will be more shallow than normal, allowing the patella to slide out of it easier. Often, the dislocation results from trauma or injury to the knee.
Due to the fact that this condition is often genetically inherited, the breeding of affected dogs is highly discouraged. Unfortunately, there are currently no proven preventative measures for patellar luxation. We recommend that if you have a breed of dog that you know is prone to this condition, have your veterinarian do a thorough orthopedic exam of the knees. Early or mild cases should limit the amount of jumping or romping around with other dogs so it doesn’t become worse!