Abstract:
The participants with knee hyperextension demonstrated poorer stance stability. Even though the patterns of postural response of the hyperextended knee participants were comparable to normal knee participants, the neuromuscular control was unknown. The ability to detect the knee joint position which could be the explanation why the two groups of participants exhibited different stance stability was still inconclusive. The current study was conducted to investigate and compare the postural and neuromuscular responses at the knee joint between participants with knee hyperextension and normal knee participants. Furthermore, the ability to detect knee joint position was also investigated. Thirty-six healthy female participants were recruited in the study, 18 normal knee and 18 hyperextended knee participants. The activities of the muscle around the knee joint were recorded with the surface electromyography and the knee joint angles were recorded with electrogoniometer while the participants were standing quietly or with the perturbation of either the visual or somatosensory systems, or both. Afterward, the ability to detect knee joint position sense was investigated with the memory-based, ipsilateral active joint position sense matching task. The absolute, relative, and variable errors from the joint matching tasks were then reported. All data were recorded from the non-dominant legs.
The results revealed comparable knee flexion responses to sensory perturbations in both groups except the knee extension response of the knee hyperextension group in the firm eyes-closed condition. Medial hamstrings muscle activity was found significant difference between the two groups in the firm eyes-closed condition (p = 0.047). The variable error which reflect the reliability of the joint matching task was found significant difference (p = 0.017) while the absolute and relative errors were not. It might be concluded that the neuromuscular control of the hyperextended knee participants were comparable to the normal knee participants only when they could access to the visual information. Despite the different muscle activation patterns, the knee joint postural adjustments were comparable. Lastly, the hyperextended knee participants had lower knee joint position sense reliability.
