The anterior cruciate ligament may be ruptured when the knee is hyperextended, hyperflexed and rotated inwards, or forced into excessive valgus. The functional anatomy of the ligament is described, and reasons for the decompensation of the knee are considered. A brief historical review of ligament repair and reconstruction is presented before outlining the clinical assessment of this common sports injury. Both autogenous and prosthetic surgical reconstruction are considered briefly although the emphasis is still upon conservative management in the majority of these cases. Lastly, a plea is made for the prevention of incidents which may lead to rupture of the ligament.