Fibular collateral ligament tear from varus impact injury ( RID2798 ) The FCL is an important resistor against varus stress for the knee. Tears of the FCL are unusual as impact on the medial knee isnt nearly as common as a lateral (valgus) impact. The other leg usually protects against varus impact. One way to do it is to start crossing a street and get hit by a car. In this case you can see the medial soft tissue contusion indicating varus impact.