Are they the same thing? Are they inherited? Would you ever breed a dog with them?

Sorry a newbie here - teach me - don't flame me!
Thanks

Here ya go --
PATELLAR LUXATION


What to Know....What to Do

by Pam Voit





In the dog, the patella is a small bone found in front of the stifle joint that is held in place by ligaments. The term "patella luxation" or "slipped stifles" is the slipping or dislocation of this tiny bone from the groove it normally rests within. The groove is called the " trochlea " and is formed by the lining up of the femur and tibia along with the attachment of the patellar tendon. The job of the patella is to protect the large tendon of the thigh muscle as it slides over the front of the femur as the muscle is used to straighten the knee joint. You can feel this for yourself by using your own knee joint. Place your hand over your kneecap and then straighten and bend your knee. You should be able to feel your kneecap sliding up and down in the trochlea.











The luxation or dislocation of the patella occurs when these parts do not line up properly. When the patella is luxated, the thigh muscle is unable to extend the knee properly which will result in lameness or an abnormal gait. Also, the slipped patella can become damaged as it rubs against the femur instead of resting in the smooth trochlea. This constant rubbing of bone to bone can lead to the degeneration of the joint and arthritis sets in as time goes by. Another problem caused by the luxation is the pull on the tibia. Over time this will cause further and further rotation of the tibia and increase the severity of the problem. In addition, the misalignment of the bones may cause sufficient strain to eventually cause ligament ruptures.

There are two directions the malformation can take. Luxation may be medial which means the tibia is rotated to the inside causing the patella to rest on the inner surface of the femur or it may occur laterally which is to the outside. Medial luxation is far more common than lateral luxation and represents almost 80% of the cases. Both legs are commonly affected and animals appear to be affected by the time they are around 6 months of age.

Patellar luxation is a common orthopedic problem for the smaller breed dogs. Studies have shown that small dogs (that is dogs weighing under 20lbs at maturity) have twelve times the chance of having this problem than medium or large to giant breed dogs. Research has also shown that females are one and a half times more likely to be affected than males.The higher cases in females may be related to the X-link factor or due to hormonal changes. Studies have suggested patellar luxation to be a recessive method of inheritance. All cases other than cases resulting from trauma are either known to be heritable or are strongly suspected to be.

The signs of patellar luxation can show up as early as weaning or can go completely undetected until late in life depending on the severity. Clinical signs can vary drastically depending on the degree of the luxation. These signs include intermittent lameness in the rear leg with the dog shifting from one leg to the other as well as the inability to straighten the stifle fully. Depending on the severity, the dog may hop, skip or even carry the leg for periods of time. With the slipping of the patella the dog will hop or skip and with an extra hop straighten its stifle to make the patella pop back into place. In some the leg is carried with the stifle flexed and the foot will touch down every third or fourth step. Others may have a crouching or bowlegged stand. The feet will be turned to the inside and most of the weight is carried on the front legs. In severe cases, the permanent luxation does not allow the thigh muscle to effectively extend the stifle. There can be pain in some of the cases.




Grades of Luxation

There are four grades of luxation and they are as follows:

Grade One: With grade one there is intermittent patellar luxation that can cause the dog to carry the affected limb occasionally. The patella easily luxates at full extension but returns to the groove when it is released. There is minimal rotation of the tibia.

Grade Two: With grade two there is frequent patellar luxation which in some cases can become more or less permanent. The dog will sometimes carry the affected limb but will bear weight with the stifle slightly flexed. The patella is easily luxated manually and remains luxated until replaced. Rotation of the tibia is present.

Grade Three: With grade three the patella is permanently luxated but can be replaced manually. The dog will often use the affected leg but not at full extension. There is marked rotation in the tibia.

Grade Four: With grade four the patella is permanently luxated and cannot be replaced manually. The dog carries the affected limb or uses it in a crouched position. Extension of the stifle is impossible. The tibial rotation is severe and results in a bow-legged appearance.




Diagnosis

Diagnosis is fairly simple for a veterinarian trained in orthopedics. The joint must be palpated and the patella manually luxated. Xrays can be used as well to determine the degree of rotation. Owners and breeders can be taught to palpate the stifles but much care must be used to avoid injury or even an incorrect diagnosis. Diagnosis in severe cases can possibly be made as early as the age of weaning, but in most cases the joints should be tight enough at 4-6 months to afford reliable palpation.

Most grade one to grade two affected dogs can make fine pets and can get along without surgical treatment. Though in later life there may be some arthritic changes requiring a pain reliever. Grade three and four affected dogs will need surgical correction of the deformities. Many techniques are available depending on the severity. Results are usually satisfactory if the degeneration has not progressed too far and once the problem is repaired, most dogs will make satisfactory pets.




What to Do

If you are purchasing a new puppy, educate yourself on the breed you are interested in. Talk to many breeders and ask questions. Check out the puppy carefully and take it to the vet as soon as possible after you have purchased it. If there is a history of patellar luxation in the breed you should make sure the breeder you are working with has certified his/her breeding stock and get a guarantee for replacement if the puppy shows up to be affected. Mildly affected puppies can serve as fine pets and can live a comfortable life so keep this in mind if you are purchasing a pet quality animal. The best thing you can do for you and your new or potential puppy is to be educated.


What breeders should do

If you are a breeder of a breed that has a history of patellar luxation you must first educate yourself on the condition. Once you have the facts, you need to study your pedigrees and your breeding stock. All breeding animals should be examined before being bred and at one year of age for certification. If found to be affected they should be graded and the information stored in a proper registry. The Orthopedic Foundation for Animals has a Patellar Luxation Registry that will gather and store data and certify your breeding stock. Only certified "normal" or "clear" dogs should be used in the breeding program. This is the only way to rid your breed of this genetic disease. Puppies should also be pre-evaluated before leaving your kennel for their new homes. This pre-evaluation can greatly help the breeder determine the future breeding potential of the puppy or assess the quality of the dog...ie show quality or pet quality. If your breed shows many cases of patellar luxation, you as a breeder, must do everything in your power to produce only the healthiest dogs possible. Certify your breeding stock and your puppies and spay or neuter any affected dogs before placing in homes or at the very least sell them as pet quality on a spay/neuter contract. As long as you breed affected animals....you will get affected animals. Break the chain now!


Update

As I update this page once again.....now 2004.....

It is unfortunate I must say that there are breeders out there NOT breaking the chain and continue to breed affected animals. We are seeing more and more cases of Patellar Luxation due to these careless breeders who think they know more than the vets and think they can continue to breed these affected animals and still rid the breed of the problem eventually. This is not going to happen...as I have watched and waited and still I am hearing more and more cases coming up.

To my dismay there are many breeders stating it is okay to breed dogs that have grade 1 or grade 2 slipped stifles. They have their breeding dogs vet checked/certified and even if their knees are graded at 1 or 2......they classify the dogs as NORMAL. They even state in their contracts on the sale of a breeding dog that grade 1 or grade 2 is normal and may be breed - they will not replace a breeding dog that is found to have patellar luxation. ...astonishing!

I will state this again - a dog with grade 1 or grade 2 slipped stifles makes a fine pet but should NEVER be used in a breeding program. Don't be fooled!

Ask a lot of questions and make sure the puppy you purchase is not from affected parents and has been evaluated before you take him home.

AWESOME! Thank you very much.

For labs diagnosed with patellar luxation requiring surgery, it's important to go to an ortho vet who has experience doing this type of surgery on larger breeds.