Patella Luxation

Luxation of the patella (knee cap) is a common developmental disorder seen in dogs and rarely cats. The patella can luxate medially (towards the inside of the knee) or laterally (towards the outside the knee). This condition usually occurs in small breed dogs where the patella luxates medially. When the patella luxates an owner may notice or feel a pop in the stifle (knee). Typically lameness is associated with a patellar luxation. An owner will usually describe a lameness that is acute and will cause their pet to hold the rear leg up close to the body. The pet may then extend the stifle causing the patella to relocate into its proper position. The lameness may then resolve but most likely recur if the patella luxates again from its proper position. A typical report is that the patient may walk normal and then skip a few steps holding the rear leg up and then use it again.

Careful examination of the stifle is needed to assess the patella along with the surrounding ligamentous structures. This examination may be needed under sedation to allow the veterinarian to better assess the stifle while the patient is relaxed. Radiographs (X-rays) are also helpful in diagnosing this disorder along with giving the veterinarian a better overall assessment of the conformation of the stifle. Below is a radiograph of a dogÕs stifle with patellar luxation. This view is taken from the front to the back of the stifle commonly referred to as a cranial caudal view. An arrow denotes the patella luxated medially. The next figure is a drawing showing a normal stifle with the patella in the proper position.

Surgery can be performed to help realign the stifle to allow the patella to move in its proper position. As the patella continues to move in an abnormal position it can cause damage to the cartilage of the stifle along with predisposing the patient to developing osteoarthritis.