Relationship of leg muscle strength and knee function in the early period after anterior cruciate ligament reconstruction

The purpose of this descriptive study was to assess the relationship between knee function and the strength testing performance of various leg muscles in the early period after anterior cruciate ligament reconstruction (ACLR). Twenty-four patients who had recent ACLR (seven females and 17 males, mean age=27 years) were tested for leg muscle strength and knee function 2 weeks after surgery. The concentric peak torques of the hip and knee extensors and knee flexors were measured at 210degrees s(-1). In addition, the latter two muscle groups were measured at 60degrees s(-1), and also isometrically (at a knee angle of 60degrees). Knee function was assessed using a three-dimensional motion analysis system combined with a force platform. This system determined knee joint angles, torques and powers during level walking, stair ascent and stair descent. Pearson's correlation coefficients were calculated to assess the relationships between the injured knee function variables and the injured/uninjured strength ratios. The correlation coefficients ranged (in absolute value) from 0.03 to 0.81, and were generally higher for the stair tasks compared with level walking, and highest for the knee extensors (as compared with the knee flexors and hip extensors), and the strength test velocity appears much less important than the muscle group tested. These results contribute evidence indicating the importance of knee extensor strength to knee function in the early period after ACLR.