The knee may be thought of as a living pulley, cable and lever system. The kneecap is perfectly centered along the axis of the hind leg. As a result, the forces that pull on the kneecap, and the forces that pull on the attachment of the tendon to the shinbone are centered and parallel to the axis of the hind leg. As the leg moves, the kneecap smoothly slides up and down in its groove. This arrangement is both stable and strong, and allows for precise control.
Bone is a dynamic living thing that is constantly breaking down and remodeling.
Consequently, bone responds to the external forces that act upon it. If a tendon pulls toward the middle, then the bony attachment of the tendon will slowly remodel itself till it too deviates toward the center. Not only is this a major factor in patellar luxation, but it is also a primary reason to correct it before it worsens. The degree of bone remodeling and rotation is also evaluated. Based upon these and other observations, a surgical procedure or a combination of different surgical procedures may be chosen to correct the patellar luxation.