Strength Assessment in Athletes following an Anterior Cruciate Ligament Injury

The anterior cruciate ligament injury is one of the most common injuries in athletes. A limited range of motion, abnormal gait mechanics, quadriceps and hamstring muscles strength loss, and very often a decreased return to pre-injury levels of activity are concomitant to ligament reconstruction. Tremendous efforts have been made over the past two decades toward an accelerated rehabilitation in order to minimize the functional and mechanical knee instability as well as quadriceps and hamstring muscles strength loss. Various strength test protocols have been employed to determine the magnitude of reduction in muscle strength, and to provide criteria for an athlete’s progression through the phases of recovery. However, since it is only the open kinetic chain feature that enables specific quantification of strength deficits in isolated muscles, this manuscript will focus on the methods for strength assessment which utilize unilateral OKC movements. By summarizing the principles and methods for strength assessment (isokinetic, isometric and isoinertial), we aimed at providing a comprehensive understanding of the current state of research that could guide the clinicians in conducting reasoned interventions.