Learning issues 1. How common is cranial cruciate ruptures or tears in a Laboradors? Very common. 2. What is a severe cranial drawer? What is in within normal limits? What does a 5mm cranial drawer signify? 1-2 is normal. 4-5 is considered marked. 3. What exactly causes joint effusion? A rupture of the ligament will lead to cell injury. Synoviocites release inflammatory mediators. The vasculature becomes more permeable resulting in increased fluid production. 4. What conformational defects will predispose the animal to cranial cruciate rupture? We couldnŐt find any literature on specific conformational defects leading to CCL rupture, but think conditions such as hip displasia, congenital patella luxation or obesity would put continuous abnormal stress on the stifle and strain the ligaments within the joint.