Tag Archives: patella luxation

Vet Lessons

I had an interesting case the other day which made me think how cool it would have been to learn about, well, interesting cases when I was applying to actually be a vet. So that’s the inspiration for this little feature: an interesting vetty subject to get your teeth into around coursework, exams, and other stuff that passes the time 🙂

The first topic is…..

Luxating Patella

I saw a 1 year old CKCS (Cavalier King Charles Spaniel) bitch for X-rays under anaesthetic due to a history of intermittent lameness on her left hind leg. The vet who examined her initially thought she might have some back pain and so booked her in for X-rays to delve deeper. On taking a look at her before we knocked her out (medically, I hasten to add) I noticed that her left knee-cap (patella) wasn’t sitting where it should, which was within the trochlear groove, which is basically the channel that runs over the end of the femur and  directs the pull of the large muscles of the hind leg over the knee (stifle) joint to insert onto the tibial crest on the tibia, resulting in extension of the lower leg. This little dog’s patella, however, was sitting to the inside of the knee, and although I could easily move it back into place, every time she flexed (bent) her stifle, it popped back to it’s abnormal position (luxated).

X-rays of her spine, pelvis, hips and stifles were all normal, and her right patella was normal. There are four grades of patellar luxation, with grades 1 and 2 not requiring any intervention. This case was a grade 3 and so will benefit from surgery to a) deepen the trochlear groove – think of it like having an egg on a saucer versus then placing it in a bowl where it will be much more likely to stay – and then b) shift the tibial crest with the muscle insertions still attached over to a new position and fix it there with a pin, so that the direction of the pull of the muscles is along the correct line, resulting in less pull to luxate the patella. Pretty cool stuff!