SummaryThe complete tear of the anterior cruciate ligament initiates the clinical syndrome represented by continued functional disability. The precise degree of functional disability is highly debated. Agreement is elusive due to the lack of uniform and scientific meth-odology. An historical review and analysis of functional and subjective rating systems is reported, and the strengths of previous systems are identified. A subjective and functional rating system is proposed in which 6 activity levels are related to pain, swelling, giving-way and overall activity. This is important because of the marked dependence of the functional disability of the anterior cruciate insufficient knee on the activity level of the patient. Thus, activity levels must be rigorously and comprehensively defined.In addition, we propose the utilisation of a risk factor checklist, based on the statistics drawn from our previous articles, to identify those patients at significant risk for future joint arthrosis. Risk factors are grouped under the categories of activity level, symptoms, clinical laxity, meniscal damage, lower limb alignment, tibiofemoral crepitus, patellofe-moral factors, rehabilitation and patient compliance.Thirdly, we examine controversial aspects of the anterior cruciate ligament syndrome existing in the literature today and demonstrate why contrasting opinions are not mutually exclusive.Finally we propose our treatment guidelines for management of the acute and chronic anterior cruciate ligament insufficient knee.