Sesamoidean Derangement in the Dog and Cat

Kenneth A. Johnson

Amongst the interesting selection of articles in this issue of the journal, three concern the patella. Notable as being the largest sesamoid bone of the body, this humble sesamoid bone is a frequent contributor to stifle joint pathology in dogs and cats. Located in the tendon of insertion of the quadriceps femoris muscle, it acts as a fulcrum, gliding in the femoral trochlea during stifle joint extension. Interestingly, many marsupials such as the kangaroo and the koala and some possums lack an osseous patella. Instead, they have a patellar-shaped pad of fibrocartilage in this location. One explanation for this species difference is that a non-osseous ‘patella’ is more resistant to fatigue fracture with repeated loading, as may occur in cats.

Patellar luxation, and to a lesser extent patellar fracture, are common; they may cause hindlimb lameness or exist as undiagnosed abnormalities. There is a growing body of literature on the surgical correction of patellar luxation, providing us with multiple effective procedures for correcting this disorder. Malalignment of the combined patella-quadriceps complex no doubt contributes to medial or lateral patellar luxation, but the role of patella alta and patella baja is not so clear.

Two of the studies in this issue of the journal concern the proximo-distal position of the patella relative to the canine stifle. The third computed tomography study on the feline stifle found that block recession trochlear plasty alone is not effective in maintaining the patella, and that ostectomy of the medial and lateral margins of the patella was necessary. Ongoing research is required to elucidate the complex pathogenesis of patellar disorders in dogs and cats.