What is Medial Patella Luxation?
The Patella, also known as the kneecap, is a bone of the knee, which sits in the tendon of the quadriceps muscle. In order for the knee (or stifle joint) to extend and straighten, the quadriceps muscle must pull on the tibia. The quadriceps tendon is maintained in front of the stifle joint by the patella, which is held in a groove of the femur, known as the trochlea. As the knee extends and flexes, the patella slides within the trochlea. Medial Patella Luxation is a disease where the patella moves outside the trochlea and slips to the inside of the leg. This condition primarily affects small dogs, such as Chihuahuas, Pomeranian's, Miniature Poodles, and Maltese Terriers. However, some larger breeds of dogs may also be affected. In about 50% of dogs, both legs are affected. Patella luxation can commonly result from a congenital or developmental misalignment of the extensor mechanism within the knee, but also occasionally occurs due to a traumatic injury.
How is Medial Patella Luxation Diagnosed?
Diagnosis of patella luxation is based on your pet’s history and a physical examination. As the grade of patella luxation changes, so too can the clinical signs that are seen. These signs may vary and may be initially seen as mild lameness and intermittent ‘hopping’ or ‘skipping’ whilst carrying the affected leg for a few steps. In this scenario, shaking or extending the leg may be seen, prior to regaining use of the leg. As the disease progresses, severe lameness and the inability to extend the knee may be seen. If left untreated, secondary changes in the joint may occur, including osteoarthritis and cranial cruciate ligament disease.