Luxating patella
A luxating patella, sometimes called a trick knee, is a condition in which the patella, or kneecap, dislocates or moves out of its normal location. It can be associated with damage to the anterior cruciate ligament.[1]
Luxating patella
Trick knee, subluxation of patella, floating patella, floating kneecap
Patellar luxation is a common condition in dogs, particularly small and miniature breeds.[2] The condition usually becomes evident between the ages of 4 and 6 months. It can occur in cats, as well, especially domestic short-haired cats.[3]
There have been several reports of patella luxation in other species such as miniature pigs, alpacas, llamas, cattle and goats.[4]
Causes[edit]
Rarely, it can be caused by some form of blunt trauma, but most frequently, it is a developmental, congenital defect. In congenital cases, it is frequently bilateral. The condition can also be inherited through genetics. This can also be caused by obesity.
Treatment[edit]
Grades II, III, and IV require surgery to correct, if the animal has difficulty walking. The surgery required is governed by the type of abnormality present, but often involves a sulcoplasty, a deepening of the trochlear sulcus where the patella sits, a realignment of the attachment of the patella tendon on the tibia, and tightening or releasing of the capsule on either side of the patella, according to which side the patella is slipping. Some grade IV conditions may require more involved surgery to realign the femur and/or tibia.
A therapeutic dosage of glucosamine can be used as a preliminary treatment to strengthen ligaments and the surrounding tissues of the joint and can delay or prevent surgery.[6]
Additional help can be given with the use of pet ramps, stairs, or steps. These can help the animal travel from one place to another, especially up and down, without adding any pain or damage to the patella.
In animal breeds[edit]
Most cases of patellar luxation are medial, and this is frequently a congenital problem in toy- and miniature-breed dogs.[7] Breeds showing a predisposition for medial patellar luxation include miniature and toy Poodles, Maltese, Jack Russell Terriers, Yorkshire Terriers, Pomeranians, Pekingese, Patterdale Terriers, Chihuahuas, Cavalier King Charles Spaniels, Papillons, Boston Terriers, Plummer Terriers and Teddy Roosevelt Terriers. Large-breed dogs are also affected, and the Labrador retriever seems particularly predisposed.
Patellar luxation is less common in cats than in dogs. Predisposed breeds include the Devon Rex and the Abyssinian. Although the specific cause of patellar luxation is unknown in these cases, a defect in hind limb conformation is generally agreed to be the underlying cause.[8]