Anterior Cruciate Ligament Injury: Compensation during Gait using Hamstring Muscle Activity

Previous research has shown that an increase in hamstring activation may compensate for anterior tibial transalation (ATT) in patients with anterior cruciate ligament deficient knee (ACLd); however, the effects of this compensation still remain unclear. The goals of this study were to quantify the activation of the hamstring muscles needed to compensate the ATT in ACLd knee during the complete gait cycle and to evaluate the effect of this compensation on quadriceps activation and joint contact forces. A two dimensional model of the knee was used, which included the tibiofemoral and patellofemoral joints, knee ligaments, the medial capsule and two muscles units. Simulations were conducted to determine the ATT in healthy and ACLd knee and the hamstring activation needed to correct the abnormal ATT to normal levels (100% compensation) and to 50% compensation. Then, the quadriceps activation and the joint contact forces were calculated. Results showed that 100% compensation would require hamstring and quadriceps activations larger than their maximum isometric force, and would generate an increment in the peak contact force at the tibiofemoral (115%) and patellofemoral (48%) joint with respect to the healthy knee. On the other hand, 50% compensation would require less force generated by the muscles (less than 0.85 of maximum isometric force) and smaller contact forces (peak tibiofemoral contact force increased 23% and peak patellofemoral contact force decreased 7.5% with respect to the healthy knee). Total compensation of ATT by means of increased hamstring activity is possible; however, partial compensation represents a less deleterious strategy

A purpose-built dynamometer to objectively measure static and dynamic knee torque

This paper reports the development of a purpose-built knee dynamometer (PBKD) to evaluate passive range of motion (ROM) and isometric muscle strength measurements of the knee. The PBKD uses a TorqSense rotary torque transducer and objectively measures isometric knee muscle strength in a valid and reliable manner and passive resistance to motion through range. The device and all associated instrumentation underwent dynamic and static calibration to ensure consistent and accurate measurements were obtained in terms of knee joint angular position, passive torque measures, and isometric torque measures. Eleven healthy male participants performed a knee flexion and extension task designed to evaluate knee function. The validation of the PBKD entailed measuring the consistency of measurement and accuracy of measurement. Accuracy of the PBKD was determined by comparing peak isometric muscle strength measurements against a KIN-COM machine. No significant differences were observed both passively and isometrically between cycles and between trials. This device can have widespread applications within the rehabilitation and clinical environment and could be used as a functional outcome measuring tool to distinguish pathological from non-pathological knees. The presented preliminary results indicate that reliable and accurate measurements of knee ROM and muscle strength can be obtained