Thigh Muscle Strengths in the Anterior Cruciate Ligament Deficient Knee: Isokinetic and Isometric Long-Term Results

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Abstract
The purpose of the study was to determine the long-term isokinetic and isometric muscle strength profile of the anterior cruciate ligament (ACL) deficient knees. In measurements of quadriceps and hamstring strengths in both legs a CYBEX II® isokinetic dynamometer was used. The peak torque values were recorded at low (60°/sec) and high (180°/sec) speed of isokinetic testing, and the maximal isometric extension and flexion outputs were measured at a knee flexion angle of 60°. The previously developed knee strength scoring scale was used to summarize the overall strength profile. According to 40 patients with old, untreated ACL ruptures, 8 years after the injury there was still a considerable quadriceps and hamstring strength deficit in the injured knee. The knee strength scores correlated well with the circumferential measurement of the high atrophy. In the isokinetic testing, the strength deficit in both extension and flexion was greater at high than low speed, and in flexion was statistically significant. It was concluded that in rehabilitation of ACL injuries specific high speed extension, and especially flexion exercises, are needed for efforts to prevent the tibial anterolateral subluxations and the painful giving-way symptoms of the injured knee.