Distribution of Knee Isokinetic Angle-specific Moments and Ratios

Overview

The quantification of the strength-producing capacity of the knee joint muscles by isokinetic measurement is one of the most widely used tools for monitoring and deciding whether to return to sport after ACL reconstruction. However, the isokinetic evaluation performed in current practice does not exploit all the measures offered by this exploration technique, which can lead to errors in analysis and interpretation of the results and underestimate its ability to predict a return to sport under optimal conditions. Recently, more complete analysis models than those currently in use and integrating the moment-angle relationship have thus proposed the use of functional ratios sweeping the whole amplitude of the knee joint. Baumgart proposed an analysis of the variation of isokinetic force moments at each angle after ligamentoplasty. This approach seems to be the future of isokinetic performance analyses, but for the moment this has only been used in pathological populations and on small numbers of patients (less than 40). There are therefore no reference values in healthy subjects.

Rupture of the anterior cruciate ligament is a common sports trauma injury, frequently leading to a surgical intervention. However, despite the extensive scientific literature on the subject, return to sports at a lower level is common, sometimes to the point of giving up pivoting sports. Current rehabilitation strategies and the means used tend to limit their effectiveness, as do the batteries of tests for returning to sport . One of the most widely used assessments for monitoring and decision-making on return to sport after ACL reconstruction is the quantification of the strength production capacity of the knee joint muscles by isokinetic measurement. However, the isokinetic evaluation carried out in current practice does not exploit all the measures offered by this exploration technique, which can lead to errors in the analysis and interpretation of the results . This discrepancy between the possibilities offered by this tool and its current exploitation may underestimate its capacity to predict a return to sport under optimal conditions . In clinical practice, the analysis is reduced to the consideration of two indices: the peak torques of the extensor and flexor muscles of the knee, which are compared between the two legs (right and left sides), and the ratio between the torque peak of the flexor muscles and that of the extensor muscles, this ratio being considered as a control of joint balance. More comprehensive analysis models than those currently in use and integrating the moment-angle relationship have thus proposed the use of functional ratios sweeping the knee's joint range of motion. Baumgart has proposed an analysis of the variation of isokinetic force moments at each angle after ligamentoplasty . This approach seems to be the future of isokinetic performance analyses, but has so far only been used in pathological populations and on small numbers of patients (less than 40). There are therefore no reference values in healthy subjects. The search for reference values for the torque of the muscles of the knee over the entire angular range of motion represents an important line of research to improve the objective evaluation of the neuromuscular performance of the knee and the return to sport of patients, particularly following ACL reconstruction.