A luxating patella is a dislocated kneecap. The patella (kneecap) is normally held in place by ligaments, but may become loose as the result of an injury or birth defect. Luxating patellas vary in severity and are given a ranking on a scale of grades one to four with grade four being for the most serious cases.

Luxating patellas are most common in smaller breeds. In most cases, the condition occurs in both your dogs' knees although it can impact only one knee.

Symptoms include limping, pain when walking, standing or when the knee is bent. Some dogs will also seem to hop or skip when they move. 

A luxating patella can be the result of an injury, or it can be an inherited trait.