Does the “Rule of Thirds” apply to the management of the injured Anterior Cruciate Ligament

Noyes et al were among the first to announce a treatment pathway for the management of the cruciate deficient knee over 40 years ago when they postulated “the rule of thirds” which stated that a third will require surgery, a third will require rehabilitation thereby avoiding surgery and a third will be asymptomatic. However, although each category exists it remains uncertain what percentage in terms of management can be assigned to each category. Hence the concept of the “Rule of Thirds” remains unproven. What, therefore, is the optimum management for the cruciate deficient knee.? Over the past 40 years there has been a plethora of articles in the orthopaedic literature relating to the management of the injured anterior cruciate ligament, some even contributing to the “replication crisis”, and apart from elite sports participants there is no clear consensus on which patients are more likely to benefit from surgery as opposed to rehabilitation alone. It is therefore likely that an unknown number of patients will have undergone surgical reconstruction when rehabilitation alone would have sufficed. This has contributed to a significant “grey area” in the management of the injured ACL The challenge is, therefore, to detect patients in this “grey area”. What are required are better designed studies and large multi -centre randomised controlled trials [RCT,s] that have a low risk of bias and that are powered for hard end points and a high level of evidence ,more refined pre-operative assessment in a dedicated knee clinic and the detection of the injury at the earliest possible moment before an undiagnosed injury allows progressive deterioration of knee joint function. Shared data collected from such clinics should aid in the provision of a more accurate consensus on the management of the cruciate deficient knee and each category in Noyes’ “rule of thirds” can be assigned their true value.