Ligament reconstruction risks
The major risk of ligament reconstructive surgery is failure or re-rupture of the graft resulting in ongoing instability (giving way) of the knee. This is why there is a prolonged rehabilitation period following surgery to give the graft time to incorporate into your knee. During this rehabilitation your graft is vulnerable to injury and you must be careful not to put it at risk by returning to sports before the physiotherapists give you the all clear. The risk of graft failure is around 5-7 %. Revision reconstructive surgery is possible using a different graft either from yourself or from a cadveric source.
Once the graft has incorporated it is at least as strong as the ligament you originally ruptured, and the risk of rupturing the graft is about the same as the risk of you injuring the native ligament in your other knee.