Abstract
Human extensor tendons of the hand were pulled to rupture, and the torn ends, when observed in the scanning electron microscope, appeared to be knotted, possibly owing to the denaturation of the collagen. This confirmed by fluorimetry assays of both the ruptured ends and the middle unbroken sections of the same tendons. The use of a proteolytic enzyme, trypsin, to remove the denatured material and enhance the repair of organised collagen fibres from both ends is suggested if the ruptured ends have the denatured knotted appearance commonly observed clinically.