Patellar Luxation – Kneecap
Patellar Luxation kneecap is a common congenital (animals are born with this disease) health condition in small dog breeds such as miniature and toy poodle, Chihuahua, Pomeranian, Yorkshire Terrier, Pekingese and other breeds of dogs and cats. Patellar Luxation affects both knees in 50% of all diagnosed cases.
The patellar or kneecap is a small bone buried in the tendon of the muscles of the thigh. The tendon is a band of tough, inelastic tissue that connects a muscle with its bony attachement. With this condition, the kneecap may slip out of the tendon and then slip back. Patellar luxation is graded 1 to 4 based on the severity of the defect, 1 being occasional mild lameness. As the disease progresses in duration and severity, this lameness becomes more frequent and eventually becomes continuous. In young puppies with severe patellar luxation, the rear legs often present a “bow-legged” appearance that worsens with growth.
Surgical correction of patellar luxation grades 1, 2, or 3 results generally in a successful clinical outcome, whereas surgical correction of grade 4 patellar luxations may not be as effective in young dogs.
When the luxation is left alone, it causes deformity and disorder in the growth of the affected limb. In severe cases, the limb may cease to function or cause other degenerative joint diseases (DJD) such as osteoarthritis. Early surgical correction is therefore essential, but the owners are not able to detect the disorder at an early age and surgical intervention in most cases will take place after 6 months of age.
It is still unclear what exactly causes this orthopedic problem. Possible causes include: hip dysplasia, deviation of muscles and bones to which patellar attaches, etc.