Patella (knee cap) dislocation
Claire came to us a couple of weeks ago because she was skipping on one of her back legs. She would be running along and hold one back leg up in the air and skip along with the other. This is a common problem in small breed dogs and is caused by a luxating patella or dislocating kneecap.
The muscles in the front of the thigh joint onto the top of the patella (knee cap) and then a tendon runs from the patella to a process on the front of the tibia. This should all be in a nice straight line. When the muscles contract the leg is kicked forward.
In some dogs there is a derformity or twist in the bones and this is no longer in a straight line. The patella is pulled off to the side.
The patella runs along in a groove on the femur (thigh bone) and if it keeps popping out it wears down the cartilage. The bone also remodels and the ridge that helps to hold the patella in place is worn down or completely lost.
Depending on the grade of luxation (dislocation) there are various surgical procedures to resolve the issue. If the luxation is only mild then no treatment may be required. The most common surgery is the surgery that we did on Claire.
Claire is the smallest dog that I have ever done this procedure on. She is a very small chihuahua and only weighs 1.5kg.
Claire had her joint opened and I deepened the groove in her femur. This is done by taking a wedge of bone out. Taking another slice of bone out and dropping the wedge back in. The makes the groove much deeper which helps to hold the patella back in place. Claire was so small that I had to use a special saw that filts onto a scalpel blade handle!
As well as this all of the ligaments on the outside of the joint are stretched because the kneecap is out of place so often. The ligaments are tightened up as the wound is closed and this provides additional support for the patella.
The next day Claire was up and about and even putting weight on her leg. There will always be some arthritis in her joint that will need to be managed but having the surgery will lessen the degree of arthritis that she will develop in this joint.