Betty's New Knee

As you some of you may recall Betty was the first cat we fostered for the Wootton Bassett Cats Protection in our new cat cabin.   She's a lovely cat and will one day make someone a fine feline companion.  Right now she is recovering from an operation Graeme performed on her knee 3 days ago as part of our charity work. Betty has for a long time (no one knows) had a dislocated patella or kneecap.  It meant she could not walk properly and was probably in some discomfort most of the time.  This is an uncommon problem in cats and it may have been the result of some sort of trauma or perhaps she was born this way. 

The operation involves moving the kneecap into it's normal position.  We grade the problem from 1 to 4 in terms of severity and she had the most severe form where the patella was permanently out of position and could not be pushed back into place. 

We start by taking x-rays to assess the joint. In the x-rays below you can see the kneecap highlighted in green.  The right leg is normal and as you can see the patella is displaced in the left knee.  It's important to always get 2 views at 90 degrees to each other so you can try build a 3D image in your mind.




The patella is a bone that helps one of the main tendons slide smoothly over the top of the knee.

There are various methods to try fix the problem and in this case we had to use a combination of techniques.  First we had to free the patella from inside of the leg, then deepen the groove the patella runs through on top of the leg and finally tighten the attachments on the outside of the knee. 

This is a picture of the groove (trochlea groove) after Graeme had removed a triangle of bone, deepened the groove then replaced the triangle.  The patella slides into that groove and if it's deep enough it can't slip out easily.  (click on the picture to enlarge it).  You can see that the left ridge of the groove is now much higher than it would have been previously.

Up to 50% of cases do not resolve completely although they rarely have any dislocation and most have a pain free life with good movement.

We expect Betty to remain lame for weeks to come and in a few months be running around like any other cat.  She will get arthritis in this joint but no as severely as she would have had we left it alone.

The post operative radiographs look good.