The Anatomy of a Square Knot
Wayne W. LaMorte, M.D., Ph.D., M.P.H.
Photography by Michael J. LaMorte
A square knot consists of two “throws”.
Throws are constructed by crossing the ends of the suture to form a loop and then wrapping one end of the suture around the other.
Here, the short end has been crossed over the long end to form a loop.
The short end has been wrapped around the long end by passing it under the long end and up through the loop to complete the first “throw”.
The loop for the second throw is initiated by once again crossing the short end over the long strand from right to left. [NOTE: A “granny knot” results if the short end crosses above the long end for one loop and below it for the other.]
The short end has been wrapped around the long end a second time by passing it under the long end and up through the loop to complete the second “throw”.
The knot has now been tightened, and the result is a square knot.
Each of the techniques for tying square knots (one hand tie, two hand tie, or instrument tie) achieves the same steps illustrated here.