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Tedís Tale- an article about luxating patellae

Ted is a very special dog who belongs to a man I have known for about 5 years now. I treated his last dog, Duke, for about 4 years and then Ted came along. Ted is a very sweet, nice- natured Papillon. He has very large, very hairy ears and is as light as a feather. The reason he is so special and probably a very good reason for those ears is that Ted is a hearing dog for the deaf. These animals are incredibly talented and are an invaluable enrichment to their ownersí lives.

About two weeks ago Ted was chasing a ball and suddenly went screamingly lame on one of his back legs and couldnít put it to the floor. When he got to the surgery it was painfully obvious that his knee- cap or patella had become dislocated and was sitting on the outside of his knee. With some careful manipulation his patella was put back in position and he was immediately much happier. Unfortunately this is something we see all too often in dogs, especially the smaller breeds like Yorkshire Terriers. It is called a luxating patella and varies enormously in severity.

The patella sits in a groove in the femur called the trochlea groove. As the leg moves the patella rides up and down in this groove and helps anchor the major muscles of the thigh to the tibia and keep everything in line. In some dogs this groove is too shallow to keep the patella in place and it is allowed to slip on and off. The shallower the groove, the easier, and less painful, it is for the patella to luxate. Many of these dogs are also bow- legged. This means that the there is a lot of force from the muscles tending to pull the patella out of place.

In Tedís case his groove was quite deep so it was only under extreme circumstances such as a sudden twist and turn chasing his ball that put enough force on things to pull his patella out, hence the pain. The only option for any of these dogs is surgery, the idea being to deepen the groove and tighten the joint up so that the patella can no longer come out. It is a fairly straightforward procedure and usually works extremely well. A nice, instant fix.

We booked Ted in for his op and got started. Once he was asleep and relaxed it was fairly easy to move his patella in and out of joint and see how loose it was. I made an incision down the outside of his knee and gradually got down to the joint capsule. This is a thick capsule of tissue that surrounds all the joints and holds the synovial fluid that lubricates the joint and acts as a shock absorber. In animals with loose joints this capsule becomes stretched and thickened. I cut into the capsule and this allowed me to pop the patella out of position and expose the groove that I needed to get to. I bent his knee right up to get the groove into a nice, accessible position. As you can see from the photos there is very little curve to the groove beforehand and then you can see the new depth after the rasping.

I used a rasp to rasp away the bone of the femur and deepened the groove to about 3 times what it had been. The disadvantage of doing this is that you have to remove the cartilage from the joint surface. Cartilage is very smooth and helps the various parts of any joint glide over each other. Once the cartilage has been removed you do get a little more friction but this doesnít cause too much trouble long term. In larger dogs there is a technique you can use that conserves some cartilage but Tedís knee was simply too small to allow it.

Once I was happy that the groove was deep enough to solve the problem I closed everything up and stitched the capsule together so that the edges overlapped. This helps to tighten everything up again because the capsule had become stretched.

After operations like this there is no need for plaster casts or big dressings. In fact, ideally you want the dog to start using the leg and moving the joint as soon as possible. If the leg stays till for too long you can get severe muscle contraction and the leg seizes up. The other problem with little dogs like Ted is that it is incredibly easy for them to run about on 3 legs. They can quickly get used to not using their leg and it becomes increasingly difficult with time to get the use back.

I saw Ted two days later for a post- op check and he was doing very well. He was already starting to bear weight on the leg and was managing to have a poo when he needed to! His owner was pleased with his progress and Ted didnít even seem to upset at being back in the surgery. A couple of treats soon convinced him that I wasnít as evil as he might have thought.

The plan for the next few weeks is to gradually increase the amount of exercise that Ted is allowed to do and that should be it. His other knee is also a little loose but sometimes you find that if that if the worst one is repaired the other one can be left so hopefully he wonít have to go through anything else. As a hearing dog he canít even really have any time off work because his skills are so essential. Iím sure in a few weeks he will be right as rain will soon be chasing his ball again.

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