Patella Luxation, trick Knee, subluxation of Patella, or floating Kneecap

A Luxating Patella, or dislocated-,moved out of it's place or slipping kneecap, is the most frequent orthopedic problem found in the Papillon / Phalene Breed, and is common in other Toy Breeds. First signs can be seen at the age of 4-6 months.

 Most frequently, it is a developmental congenital defect. In congenital cases, it is frequently bilateral (on both hind legs). The condition can also be inherited through genetics.
Patella luxation is graded into 4 categories: from mild to severe.
Symptoms of a Luxating Patella in either one, or both hind knees, is lameness. the lameness can be showing up only on occasions, or can be continuous.

A veterinarian can palpate the knee(s),  to see if it slips inside the joint more than it would  be normally expected.
The milder form of Patella Luxation can frequently be treated with anti-inflammatory medications and exercise restriction.
If the lameness is continuous and the joint is unstable,( severe form of Patella Luxation) surgery is needed to correct the problem.