The concept of skeletal muscle spasm is widely used despite the fact that a generally accepted definition of this term does not exist. Nevertheless, the clinical literature dealing with such diseases as poliomyelitis, arthritis, low back pain and many other conditions abounds with articles in which the term spasm is persistently used. It is commonplace on medical and orthopedic ward rounds and has even assumed medicolegal sanction. Such a commonly held concept ought to have a clear and concise pathophysiologic basis, easily understood and agreed on by all. Yet a search of the literature and especially of textbooks of physiology, neurology, orthopedics and medicine fails to reveal any but the vaguest explanations not only of the word spasm but even of the related concepts of tonus or tone.1 To make matters worse, spasm is often confounded with rigidity, spasticity, spasms, contracture (histologic or physiologic) and cramp.
HARELL A, MEAD S, MUELLER E. THE PROBLEM OF SPASM IN SKELETAL MUSCLEA Clinical and Laboratory Study. JAMA. 1950;143(7):640–644. doi:10.1001/jama.1950.02910420028009