Learning Issues: 1) How common is cranial cruciate ruptures or tears in Labradors? --Very common 2) What is a severe cranial drawer? What is within normal limits? What does a 5mm cranial drawer signify? In a normal stifle joint no cranial drawer sign is seen, but 1-2mm of movement can be within normal limits. A 4-5mm sign definitely indicates damage, either stretching or tearing, of the cranial drawer. 3) What exactly causes the joint effusion? 4) What conformational defects could cause cranial cruciate rupture?