Management of medial patellar luxation in dogs: what you need to know

The patella is an ossification in the tendon of insertion of the quadriceps femoris muscle. It works along with the femoral trochlea as a pulley, redirecting the line of action of the quadriceps tendon. For the patella to be stable and to move in the most efficient direction, axial alignment of the extensor apparatus with the underlying skeletal elements is necessary. The extensor apparatus is composed of the quadriceps femoris muscle, which originates in the ventral aspect of the ilium and the proximal femur. It converges on the patella, and continues as the patellar ligament, which finally attaches to the tibial tuberosity. Other periarticular elements, such as joint capsule and femoropatellar ligaments, also increase the stability of the femoropatellar articulation. Medial patellar luxation (MPL) is one of the most common diseases affecting the canine stifle. Although it can be seen in large-breed dogs, including Labradors, smallbreed dogs are more commonly affected, with Yorkshire Terriers and poodles over-represented. It is also remarkable that MPL is more common than lateral patellar luxation (LPL), representing 75-80 per cent of cases and reaching up to 98 per cent in small breeds, according to some research. Bilateral MPL affects 20-25 per cent of all MPL cases, but some authors increase this percentage up to 50-65 per cent. Regarding large breeds, although MPL is more frequent as well, the percentage of LPL in these breeds is higher than in small-breed dogs. In terms of sex predisposition for MPL, small-breed females and largebreed males are more affected. In cats, MPL is also more common than LPL.