Rahimi, Seyed Mohsen
Reflexes elicited by per-cutaneous stimulation of the medial and lateral ligaments of the knee.
PhD thesis, University of Glasgow.
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Joint disease is common in adults and in adolescents. It particularly affects the knee joints. In young people, joint disease has a number of causes including: genetic factors, defects in joint cartilage and sports related injuries. In particular, overtraining and traumatic injuries are common in many sports Participation in sports has expanded during the last two decades in many parts of the world. This has led to an increased number of injuries. Our knowledge of the role of ligaments in the control of movements and how they should be managed after injuries needs to expand as fast as participation rates. The aims of the current study were firstly, to investigate if reflexes can be elicited by electrical stimulation of ligaments. Secondly, to investigate if different muscles are affected differently by these reflexes. The final aim was to investigate if these reflexes can be modulated by posture or muscle activity. A total of 44 volunteers participated in a series of experiments. These experiments were designed to elicit reflexes following electrical stimulation of the collateral knee ligaments during sitting, standing and walking on treadmill. The reflexes were observed in averaged rectified electromyograms from Rectus Femoris, Vastus Medialis, Vastus Lateralis, Lateral and Medial Gastrocnemius and Soleus. Muscle activity was essential if reflexes were to be elicited. No reflexes were elicited in relaxed muscles. During the first series of experiments reflexes in Rectus Femoris, Vastus Lateralis and Vastus Medialis were investigated while the Reflexes were identified as changes in the averaged rectified electromyograms (EMG). The EMG in the immediate post stimulus period was compared with the pre-stimulus control. Inhibitory and excitatory reflexes were elicited following ligament stimulation in all three sets of experiments. The mean latency in quadriceps for early excitation was 57 +/- 6 msec and 67 +/- 10 msec for early inhibitions. The equivalent means were 70 +/- 6 msec and 77 +/- 6 msec for triceps. The shortest latency recorded in quadriceps was 46 msec. Longer latency reflexes were frequently observed. The mean latency in quadriceps for late excitation was 102 +/- 6 msec and 113 +/- 11 msec for late inhibitions. The equivalent means were 110 +/- 6 msec and 119 +/- 11 msec for triceps. There was no significant difference in the latencies of reflexes from MCL and LCL. The latencies in triceps were approximately 10 msec longer (90 msec for quadriceps a 100 msec for triceps) than those in quadriceps and this can be attributed to their longer conduction pathway. The reflexes were also recorded during gait. During walking, the latencies of both excitations and inhibitions were significantly longer than they were during sitting and standing. The mean latency of excitatory reflexes in Vastus Lateralis after LCL stimulation were 71 +/- 5 msec. For inhibitory reflexes the mean latency was 87 +/- 1 msec. The mean latency for excitation reflexes in Lateral Gastrocnemus was 82 +/- 2 msec and for inhibition reflexes was 94 +/- 3 msec. In each set of experiments the shortest latencies were consistent with slow group II or group III afferents excited by relatively strong stimulation. Control experiments using topical cutaneous anaesthesia minimised the possibility of cutaneous contributions to the observed reflexes. It is also possible that the electrical stimulation excited capsular afferents located close to the ligaments. This cannot be settled by the experiment reported in this thesis and the observed reflexes are best described as ligamento-muscular reflexes. These observed effects are consistent with recent results already published by Kim et al in 1995.
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