Since the simultaneous publications of Erb1 and Westphal,2 in 1875, on this subject, the knee-phenomenon has attracted a great deal of attention on the part of the profession, both as to its nature and its clinical significance. Erb termed the phenomenon the patellar-tendon reflex; Westphal the knee-phenomenon; while the English usually speak of it as the knee-jerk. Each of these terms is in common use, signifying alike the contraction of the quadriceps femoris muscle and the forward jerk of the foot, when a sharp blow is struck upon the ligamentum patellœ.
The question of the nature of this phenomenon need not detain us long. The views originally expressed by Erb and Westphal still divide the opinions of the profession. Erb believes it to be true reflex action, a peripheral impression being conveyed to the centre in the spinal cord, and thence a motor impulse transmitted
ZENNER P. THE VALUE OF THE KNEE-PHENOMENON IN THE DIAGNOSIS OF DISEASES OF THE NERVOUS SYSTEM.. JAMA. 1886;VII(2):32–35. doi:10.1001/jama.1886.04250070040002
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