An investigation of reflex elicited by percutaneous stimulation of the medial and lateral ligaments of the human knee

Introduction: Disease and injury of joints are major causes of pain and disability in the population. The principal purpose of this study was to extend our knowledge of reflexes associated with joint. Methods: Seventeen subjects were seated on a testing bench and hip angle was 90 degrees. The maximal voluntary contractions of the quadriceps were measured at 180 degrees of knee extension. This was then used to set the magnitude of subsequent sub-maximal contractions at 5, 10 and 20% of MVC. An identical stimulation sequence was delivered during sustained contractions. Electrodes were placed over the lateral and medial knee ligaments separately and the ligaments were stimulated by 3 pulses of 1 msec duration at 100 HZ. The stimulation intensity was the ranged of 0-45 mamps. The muscles selected were Rectus Femoris, Vastus Medialis and Vastus Lateralis. Results: No reflexes were elicited in very low current, effects have started in 20 ma. The pattern of the muscle response was relevant to the stimulation intensity. By increasing the stimulation intensity the EMG waves became bigger. In addition, the magnitudes of the responses were increased. Reflexes elicited following MCL and LCL stimulation artifact. Inhibition and excitation reflexes elicited and there was no significant difference between responses after MCL and LCL stimulation. The mean latency of early inhibition after LCL stimulation was 66+7 (ms) and After MCL stimulation was 68+12 (ms). The difference was not significant (P=0.26). Conclusion: It may be concluded that that reflexes may be elicited following enough electrical stimulation of the MCL and LCL and the muscles develop a sustained contraction. There was also no evidence to suggest that the reflexes are changed by movement from a seated to a standing posture. Stimulation of MCL and LCL seems to elicit reflexes widely in the limb and to affect muscles acting above and below the knee.