September Blog – Luxating Patellas

Patella Luxation is a dislocation of the kneecap (patella). The knee joint connects the femur, (thighbone) and the tibia (shinbone). The patella is normally located in a groove called the trochlear groove, found at the end of the femur. This condition occurs if the groove is too shallow, and when a pet bends its knee, the patella pops out of place. The main symptom of luxating patella is intermittent hopping or skipping on the limb when the patella pops out of place.

The kneecap may dislocate toward the inside (medial) or outside (lateral) of the leg or move in both directions. When the patella is luxated out of the joint, it rides against the bone instead of in the joint groove, causing pain and eventually arthritis. It is often recommended to repair sooner than later to prevent future problems. In some cases, your pet’s knee may require bone rotation for alignment, which is medically called tibial tuberosity transposition (TTT).

Many toy and small breed dogs, such as Maltese, Chihuahua, Poodle, Pomeranian, and Pug, have a genetic predisposition for luxating patellas. Medial luxation is the most common condition that affects them. Although it’s rare, cats can also have luxating patellas.

What causes luxating patellas?

• Hereditary Defect
• Congenital Malformation
• Injury

Patellar Luxation Grading Scale

Veterinarians diagnose luxating patellas using a grading system. A course of treatment will depend on your pet’s diagnosis. For example, a Grade 1- 2 luxating patella typically does not require surgery, whereas a Grade 3 will eventually need surgery. Grade 4’s need surgery, possibly requiring a specialist.

GRADE I
The kneecap can be manipulated out of its groove but returns to its normal position spontaneously.

GRADE II
The kneecap rides out of its groove occasionally and can be replaced in the groove by manipulation.

GRADE III
The kneecap rides out of its groove most of the time but can be replaced in the groove via manipulation.

GRADE IV
The kneecap rides out of its groove all the time and cannot be replaced inside the groove.