It sounds like you may have torn one or both of the ligaments in your knee. There are several different methods to repair a knee injury of this type, but no agreement about which one works the best. When treating these injuries, the surgeon tries to repair as much of the damage as possible at one time. Sometimes more than one operation is required.
The technique mentioned (using the semitendinous tendon of the hamstring muscle) has several advantages. First, when using your own tendon, it is not necessary to obtain bone or tissue from someone else. This eliminates complications from grafting. Second, the hamstring tendon travels in the same direction as a muscle called the popliteus. This gives the knee a better mechanical advantage. Third, this technique changes the way the surgeon drills through one of the bones to attach the graft. This helps prevent fractures from the drilling process.
There are several other advantages due to the fact that this surgical technique helps prevent backward movement of the lower leg bone (tibia) on the upper leg bone (femur). There are always possible problems after surgery. Ask the doctor to review these with you before making a decision.