Pain thresholds and electromyographic features of periarticular muscles in patients with osteoarthritis of the knee

Abstract

Electrical stimulation pain thresholds and EMG activity were studied, using the vastus medialis muscle of healthy control subjects and of patients with osteoarthritis of the knee. Various categories of sensation elicited by progressive increases of the level of electrical stimulation (including one defined as pain threshold) were defined for control subjects. For patients, muscular pain thresholds differed significantly for the two sides of the body; they were usually lower in the more affected side. Involuntary activity of certain motor units and delayed relaxation following voluntary contraction were consistently observed in patients. The involuntary activity was affected by limb position and by mechanical stimulation of tender areas of the muscle or joint. Differences in pain threshold between the two sides were significantly reduced and the EMG pattern became normal following treatment with injections of local anaesthetic into tender periarticular areas and systemic administration of lysine acetylsalicylate. In standing patients, abnormal EMG activity (which was characteristically sensitive to body load and its variations) was found. Injection of a local anaesthetic into the joint cavity was able to induce a rapid subjective improvement and a consistent reduction of EMG activity.

Effect of piroxicam on gait in patients with osteoarthritis of the knee

“…With pain, there is inhibition of contraction of the quadriceps muscle (17), often an early manifestation of knee disease. The consequent reduction in the flexion moment, unless offset by a reduction in the adduction moment, would result in a dynamically unstable knee (10).…”

Referred muscle pain: Clinical and pathophysiologic aspects

“…The section area of this same muscle, examined by echographic scans, was lower on the affected than on the nonaffected side. In standing position, an intense electromyographic activity of the vastus medialis was seen in the patients, which increased on straightening the trunk [64], in contrast to total absence of activity in healthy subjects in the same conditions.…”

Effects of Exercise and Physical Activity on Knee Osteoarthritis

“…Alteration in the function of soft tissue structures has been shown to independently generate pain in the affected limb. In view of this, it could be theorized that improving range of motion of the joint and the overlying muscles and soft tissue structures should improve gait mechanics, joint movement, fascial tension, and tissue circulation, as well as reduce sensory nerve sensitivity [48,49].…”