How to Teach Knot Tying:Teaching with the Kinesthetic Approach

Edward Kim, M.D., Hueylan Chern, M.D., Emily Huang, M.D., Barnard Palmer, M.D.Department of SurgeryUniversity of California San Francisco

Abstract

This guide is the product of three years of observing and teaching surgical interns at the UCSF Surgical Skills Center. At the beginning of each year, we documented the baseline skill levels of our trainees by video recording them as they tied knots and performed basic suturing tasks. When we reviewed these videos, a consistent and specific pattern of mistakes emerged. Careful analysis of these novice mistakes allowed us to deconstruct the properly tied knot into its critical elements and in turn led us to develop an innovative curriculum for teaching basic knot tying. We have found that emphasizing key kinesthetic elements in the process of knot tying significantly improves novice performance (Chern et al., 2011). We present our curriculum, including a process-based objective assessment for evaluating the results, in this manual.

Outline

1. Introduction: The Importance of the Cognitive Phase2. Objectives3. Background:

a. Context Matters: Use of Knots in Surgeryb. A Cognitive Task Analysis of Knot Tying: Understanding Root Cause of

Errors4. A Practical Glossary for Teaching Knot Tying5. A Kinesthetic Curriculum for Teaching Knot Tying

a. Suture Handling Maneuvers1) Gather 2) Slide3) Anchor/Lock

b. Optimal Starting Positionc. Tying Knots

1) Two-handed half hitches/slip knots2) Two-handed square knots

6. An Objective Checklist to Evaluate Mechanics7. Discussion8. Appendix

a. Instrument Tieb. One-handed Knot Tying

9. References

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Introduction: The Importance of the Cognitive Phase

Fitts and Posner (1967) described the acquisition of a skill as progression through three phases:

1. Declarative (Cognitive): the learner understands the components of the skill2. Associative: the steps of the skill are integrated and completed as a single

continuous task3. Autonomous: the skill becomes automatic and little or no conscious

attention is necessary to perform itLearners start by understanding the steps of a skill in the cognitive phase, proceed on to the associative phase as they continue to practice, and eventually develop mastery as they achieve the autonomous phase. A solid cognitive understanding of the task sets the basis for successful acquisition of the skill, and conversely, an incomplete cognitive grasp of a skill’s important components can lead to practice of incorrect technique. In order to teach a skill effectively, an instructor should be able to deconstruct it into its essential components without any omissions (Clark et al., 2008).

Deconstruction of a task, unless methodically conducted, can be flawed by unconscious omission of steps that seem obvious and second nature to the expert. Perhaps because surgeons view knot tying as such a simple, automatic skill, our ability to verbalize the essential components of this task is often incomplete. The traditional knot-tying curriculum illustrates the correct ways to orient, loop, and cinch the sutures to create secure knots (Rogers and Ketchum, 2007) without addressing the key process component that facilitates proper execution of those steps: manipulation of the suture to consistently obtain ideal relative lengths of the strands and maintain consistent tension on them.

This kinesthetic handling of suture is widely practiced by experts and is performed with specific, non-intuitive, maneuvers. Without explicit, declarative, instruction in these maneuvers, novices have great difficulty proceeding to the associative phase of skills acquisition. This fundamental component of knot tying is analogous to body position and balance in sports. In swimming, proper head positioning to balance the body horizontally forms the basis for further progress, while in tennis, proper footwork and body rotation are the key building blocks for achieving effective strokes. In knot tying, the proper control of suture lengths creates the stability and balance necessary for skillful performance of the task.

This manual introduces a surgical knot-tying curriculum based on kinesthetic handling of suture that provides novice surgical trainees with a comprehensive instruction of the skill. This critical component of knot tying has not previously been described in the literature and is presented here for the first time. Also included is a checklist for assessment, and multiple exercises that allow for graded difficulties and a variety of surgical contexts to stimulate situational learning (Reder, Anderson, and Simon, 1996). The curriculum is organized into multiple sessions over several weeks to allow for distributed practice (Moulton et al., 2006).

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Objectives

Objectives for learners:1. Deconstruct the task of knot tying into its main components2. Explain the key kinesthetic elements necessary for optimal knot tying3. Demonstrate proper technique for tying two-handed square knots and two-handed

half-hitches/slip knot4. Describe the most common knots used in surgery5. Compare and contrast the technique for tying a square knot and half-hitches/slip

knot

Objectives for teachers:1. Deconstruct the task of knot tying into its main components2. Explain the key kinesthetic elements necessary for optimal knot tying3. Describe how poor execution of the key kinesthetic elements can lead to error

among novices4. Utilize standard vocabulary for describing maneuvers and components of knots5. Provide specific constructive feedback using a framework based on kinesthetic

knot tying technique

Background

Context Matters: Use of Knots in Surgery

Knots have played an important role in human history starting with ropes created from plant fibers and used to build basic tools and dwellings. Among the various groups of knot users such as sailors and fishermen, surgeons are an insignificant minority with a limited repertoire of only a few simple knots among the hundreds that exist (Ashley, 1944). What differentiates surgical knot tying from other disciplines is the delicate nature of the objects being tied. Whereas sailors use sturdy ropes to tie on solid structures, surgeons use fine sutures to tie around fragile human tissue. Knots in sailing are judged exclusively on the final knot quality, but knots in surgery must not only be secure, there must also be minimal trauma to the tissue during the process of tying. If a surgeon avulses a blood vessel in the process of ligating it by erratically pulling on the sutures, he/she has defeated the purpose of the knot. Our focus on kinesthetics is therefore informed by the contextual specificity of surgical knot tying, which requires that gentle handling of the sutures be an integral part of the skill.

A Cognitive Task Analysis of Knot Tying: Understanding Root Causes of Errors

The initial impression one gets from watching novices tie knots is a sense of struggle. They almost appear to be wrestling with the sutures in an effort to subdue them into a knot. Inattentive instructors attribute the perceived clumsiness to underdeveloped muscle memory that can simply be remedied with more repetition. The default advice to “practice more” is least helpful for learners as it fails to identify and correct improper

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technique. This approach assumes that learners will eventually work through their own mistakes in a prolonged associative phase of learning.

Commenting on specific errors is an improvement over recommending more repetitions, but simply pointing out the missteps may not be enough. Some errors are manifestations of less apparent, but fundamental, underlying problems; correcting the overt errors requires focusing on the root cause. Expert recognition and understanding of a learner’s mistakes with accurate assessment and effective feedback defines the process of deliberate practice (Ericsson, 1993).

Revisiting an analogous situation in sports is instructive. A common problem seen in beginner swimmers is that their feet sink, which creates unwanted drag. The problem is easily recognized, but advising swimmers to focus on keeping their feet up only leads to inefficient over-kicking in an attempt to elevate the feet. In actuality, the problem of “sinking feet” stems from improperly high head position, which unbalances the body and tilts the feet down. Understanding this, a much more effective approach to the struggling swimmer with sinking feet is to focus on lowering head position. This shifts the swimmer’s weight forward and naturally elevates the feet, improving performance.

For knot tying, an analysis of novice knot tying conducted by Rogers, Regehr, and MacDonald (2002) identified four common beginner errors (frequency):

1. Too much motion in right hand (38%)2. Failure to maintain consistent tension (17%)3. Hands too close to knot (13%)4. Failure to cross hands (7%).

Based on these findings, a simplistic approach to feedback might comprise of the following:

1. Don’t move your right hand too much2. Try to keep a constant tension on the thread3. Don’t tie to close to the knot4. Cross your hands when you tie square knots

All these comments are valid and can be helpful to some degree. However if we look beyond the overt errors to identify the fundamental mistakes we can provide even more effective instruction. A comparison between experts and novices provides valuable insights in this endeavor. When tying knots, experts tend to:

1. Quickly manipulate the suture ends to obtain a comfortable working distance from the knot2. Maintain this distance throughout the entire knot tying process

It turns out that failure to obtain and then maintain a comfortable working distance from the knot is the root cause of the four common beginner errors. For example, novices often hold the suture ends too loosely and slide up on them, causing their relative lengths to change. The tail end of suture becomes too short to easily loop into knots, which results in fumbling, uneven tension, and the use of extra fingers to form the loop (the two most frequent errors, as observed by Rogers et al.). By teaching some key suture handling maneuvers (gathering, sliding, and locking) and emphasizing kinesthetic awareness, we can address these root causes of error and teach trainees to establish and maintain an ideal, balanced position from which it is easy to tie knots smoothly without excessive or erratic lifting, fumbling, and dropping of suture.

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A Practical Glossary for Teaching Knot Tying

A common vocabulary with clear definitions facilitates communication between instructors and trainees. To that end, we recommend reviewing the following glossary with trainees prior to commencing the knot tying curriculum:

Components of a Knot (Figure 1) Loop: part of the suture between the ends where it is intertwined on itself to form

the knot Working End (the Tail): active end of the thread passed over or under the

stationary (Standing) end to form loops Standing End (the Post): stationary end of the thread not involved in the

formation of the knot Working Distance: the distance from the hands to the knot

Figure 1: Components of a Knot

Maneuvers in knot tying Gather: to shorten the distance between the hands and the knot Slide: to lengthen the distance between the hands and the knot Anchor/Lock: to hold the suture in such a way that the distance between the

hands and the knot cannot change Form: to make a loop by passing one end of the suture over or under the other Lay down: to cinch a knot tight Throw: the entire process of forming and laying down a knot

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Types of knots (Figure 2) Overhand: a knot laid down by pulling the ends in equal and opposite (180

degree) directions Half Hitch: an overhand knot that is tumbled on its side by uneven tension on the

threads as the knot is laid down. The knot consists of a single loop, laid down by sliding the loop down the vertically held post

Slip: two half hitches laid in the same direction Square: two overhand knots thrown with opposite orientations (opposite

handedness) Granny: two overhand knots thrown with the same orientation (same

handedness). This type of knot has a tendency to unravel. The term granny knot is sometimes mistakenly used to denote two half hitches, or a slip knot

Figure 2: Types of Knots. In the first row are variations based on overhand knots, from left to right, the overhand knot, the square knot, and the granny knot. In the second row are variations based on half-hitch knots, from left to right, a single half-hitch and a slip knot.

Techniques for forming a loop Two-handed: a technique in which the hand anchoring the standing end supinates

and pronates to form loops One-handed: a technique in which the hand anchoring the standing end remains

entirely stationary throughout loop formation

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A Kinesthetic Curriculum for Teaching Knot Tying

Refer also to the accompanying video, “A Kinesthetic Curriculum for Teaching Knot Tying,” for demonstrations of the following. An online copy of the video can be found at http://youtu.be/XhTh6ke6mks for easy distribuation.

Suture Handling Maneuvers

We start by teaching the suture handling maneuvers: gathering, sliding, and anchoring/locking. As described above, these often-overlooked skills establish an optimal working distance, and build the foundation for proficient surgical knot tying.

Gather – allows the surgeon to shorten the length of the suture by a hands-width1. Start: hold the suture with only the thumb and the forefinger. The wrist

should be pronated2. Hook: supinate the wrist and use the last three digits to the hook and grab the

suture3. Let Go: release the grasp of the thumb and forefinger and hold the suture with

the last three digits4. Re-grab: pronate the wrist and re-grab the suture with the forefinger and the

thumb while releasing it from the last three digits

Slide – when used in combination with the gather, this maneuver allows the surgeon to make finer shortening adjustments of the suture length

1. Start: hold the suture with only the thumb and the forefinger. The wrist should be pronated

2. Hook: supinate the wrist and use the last three digits to the hook and grab the suture

3. Let Go: release the grasp of the thumb and forefinger and hold the suture with the last three digits

4. Slide: slide back on the suture held by the last three digits to adjust the distance from the knot

5. Re-grab: pronate the wrist and re-grab the suture with the forefinger and the thumb while releasing it from the last three digits

Anchor – used in combination with gather, this maneuver allows the surgeon to securely hold the suture

1. Start: hold the suture with only the thumb and the forefinger. The wrist should be pronated

2. Hook: supinate the wrist and use the last three digits to the hook and grab the suture

3. Let Go: release the grasp of the thumb and forefinger and hold the suture with the last three digits

4. Lock: pronate the wrist and re-grab the suture with the third digit while still holding with the fourth and fifth digits

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Optimal Starting Position

Prior to proceeding ahead to actually tying a knot, the learners should demonstrate the ability to smoothly manipulate the sutures into the ideal starting position. The learner needs to grasp the sutures with just the thumb and forefingers with the hands pronated. The dominant hand grasps the working end of the suture (the tail) about a hands-width from its end. The non-dominant hand then gathers, slides and locks the standing end (the post) when the lengths of both suture ends where they are grasped are even and at about four to six inches from where the knot will be secured.

At this point, the learners should ideally begin to appreciate the proper “feel” how to handle the sutures. The delicate and gentle quality of the gathering and sliding maneuvers should discourage excessive force and erratic movements. A helpful visual is imagery is to let the suture “flow through their hands like water”.

Two-handed Half Hitch/Slip Knots

We start the actual knot tying part of the curriculum with the two-handed half hitch knot, not the square knot. An emphasis needs to be made on this point. In addition to being a widely used knot in surgery, the half-hitch/slip knot is a cognitively simple medium for practicing the key kinesthetic elements of knot tying. Proceeding in this stepwise fashion avoids cognitive overload in the learner. (2)The learners can focus on properly forming the loops and lay them down to secure the knots. The half hitch is a simple knot with the only variation between each knot being the alternation in the loop orientation. The non-dominant hand holding the post remains relatively stationary in space, only supinating and pronating to form loops. The dominant hand works in a repetitive motion to slide the loop down along the post to lay down each knot. This exercise is ideal for teaching correct mechanics of both constant tension, ideal working distance, and crisp, efficient movements.

1. Setupa. The ideal working distance is 4-6 inches from the knotb. Securely lock the standing end (the post)c. Avoid an excessively long working end (the tail)

2. Forming the loop (Two-handed technique)a. The hand holding the post leads with the thumb or forefinger. Initiate

by crossing the post with the tail. Using only the tips of the forefinger and thumb, complete by grabbing the tail and flipping through the loop with crisp supination or pronation of the wrist.

3. Gathering the Suture to Lay the Knot Downa. After the loop has been formed, again grasp thetailof the suture with

only the forefinger and the thumb of the free hand.b. With the post held vertically, perform a gathering maneuver on the

free end to slide the loop down; use the forefinger to apply direct pressure to the suture to tighten the knot just beyond the knot itself.

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4. Stable Recoverya. A secure hold on the post maintains a stable working distance and

contributes to a seamless transition to the formation of next knot.b. The other hand should lightly slide up on the tail to about the same

distance as the post.

Two-handed Square Knot

The square knot is a more complicated knot that can when improperly tied becomes a half-hitch/slip knot. Although the loops are formed in the same way as the half-hitch, the way the knot is laid down is critical. One must pay careful attention to the relative direction of pull on the suture ends. The tension must be even and directly opposite or otherwise the knot capsizes into a half-hitch. In addition, erratic tension on the threads between knots loosens the first overhand knot and leads to the air knot as the second knot cinches down square in the loosened state. A slip knot is more forgiving and allows the second half-hitch to tighten the first knot to remove the slack. The increased complexity and difficulty are the reasons to avoid teaching the square knot as the first knot our surgical trainees who are still learning the mechanics of suture handling and knot tying.

1. Setupa. The ideal working distance is 4-6 inches from the knotb. Securely lock the standing end (the post)c. Avoid an excessively long working end (the tail)

2. Forming the loop (Two-handed technique)a. The hand holding the post leads with the thumb or forefinger. Initiate

by crossing the post with the tail. Using only the tips of the forefinger and thumb, complete by grabbing the tail and flipping through the loop with crisp supination or pronation of the wrist.

3. Gathering the Suture to Lay the Knot Downa. After the loop has been formed, again grasp the tail of the suture with

only the forefinger and the thumb of the free hand.b. Orient the hands in opposite directions according, and apply equal and

opposite tension. Perform a gathering maneuver on the tail, then use the forefinger to continue applying direct, equal, and opposite tensionto the suture while tightening the knot. In order to do this, the hands may need to cross.

4. Stable Recoverya. A secure hold on the post maintains a stable working distance and

contributes to a seamless transition to the formation of next knot.

Although many of the basic movements are the same, the mechanics of the square knot is quite different. One can easily distinguish from distance whether one is tying a square knot or a half hitch. The latter as described previously is characterized by a stationary hand that just rotates at the wrist and the other hand repeated moving down the

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thread in the same motion. When one ties a square knot, both hands are in motion and move in opposite direction that alternate with each knot. Maintaining proper working distance and constant tension on the sutures are obviously more difficult in this situation.

To further show the square knot’s potential for inflicting cognitive overload on unprepared novices, listed believe of the common questions asked when learning to tie square knots along with their respective answers for the half hitch.

Question Half hitch Square knotDo I start with the suture crossed or uncrossed?

Makes no difference Either is acceptable, but… If you start crossed, you have to cross your hands as

you lay down the second knot. If you start uncrossed, you must cross your hands as

you lay down the first knot. Does it matter whether I lead with the thumb or the forefinger on the first knot?

Makes no difference Suture starts crossed If the standing end (the post) is in front of the

working end (tail), then the forefinger leads. If the post is behind the tail, then the thumb leads.

Suture starts uncrossed Can choose either, but the finger you choose

determines the orientation of your hands when you cross on the first knot.

If you lead with the thumb, the post hand needs to cross in front of the tail.

If you lead with the forefinger, the post hand needs to cross behind the tail.

An aid to remember the correct orientation: the leading finger points towards the direction to move the hand; the forefinger points to the back and the thumb points to the back.

How to Evaluate: A Checklist to Evaluate Mechanics

The following checklist was developed and validated in our surgical skills center to assess proficiency in knot tying. The checklist focuses on the mechanics described above and can be used to provide specific feedback to correct mistakes.

1. Distance from knot (approximately 4-6 inches)2. Uses only thumb and forefinger to form knots3. Gathers the tail correctly4. Lays knot down with forefinger5. Does not drop suture6. Stable recovery (securely anchors the post)

Discussion

Knot tying is a fundamental skill in surgery that all trainees must master to progress onto more difficult and complex tasks. It is surprising and but not unexpected that the teaching of this most basic skill has remained neglected. It is fair to conclude

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that all surgeons eventually learn to tie knots whether they receive formal training or not. Most trainees “pick up” the skills of suture handling over months or years with continuing practice and exposure. Unfortunately with the current external pressures faced by surgical education, we no longer have the luxury to let our learners unnecessarily wallow in the associative phase of skills acquisition.

Knot tying can be a contentious topic among surgeons with dogma and personal preference being the basis of most arguments. Our trainees get caught in the crossfire and often receive confusing and mixed messages. One hot topic is the square knot. There is no question that the square is a better binding knot than two half-hitches, but many half-hitches work just as well as the square knot in the clinical setting. Multiple specialties and surgeons have used half-hitches without problems and this fact cannot be ignored. Our trainees obviously need to learn both types of knot and they will ultimately develop their own preferences. From an educational standpoint, I hope we have made a cogent argument regarding the need to teach both knots and the respective order.

On an even more technical note, one can argue that the gathering maneuver used when laying the knot down is an unnecessary and wasted move when the knot is on the surface. Same came be said also for always using the forefinger to cinch the knot securely. The forefinger is necessary in tying at depth, but not necessary when on the surface. We feel that making the novice decide whether to gather or not and whether to use a forefinger or not is more of an unnecessary additional cognitive burden. Both maneuvers can be done efficiently and gracefully within a second.

Lastly, some learners are taught what is best described as the two-handed, one-handed knot. The same hand the holds the post and rotates the wrist to form the loops also lays down knot. The hand holding the tail remains relatively stationary. We avoid using this techniques for the reasons cited above. The main challenge of knot tying for novices are establishing and maintaining an optimal setup. By using the same the hand that anchors the post the lay down the knot, the learner is required to re-establish the setup with each knot.

Our experience has encouraged us to examine more carefully how we teach technical skills. Although many tasks may simply require repetitive practice and exposure, there may be opportunities for significant in the quality of instruction.

Appendix

Instrument TieWith an instrument tie, the same consideration needs to be paid to maintaining a

stable distance from the knot. However since the needle driver is used here, there is no need to gather the tail (working end) when laying the knot down. The tail should actually be kept short to easily allow the learner to pull the suture through the loop. Laying down the knot flat is much easier with an instrument and crossing the ends to lay down square knots is also easier.

One-Handed Knot TyingThe post is held stationary and the free hand both forms and lays the knot down.

The distance from the knot should still be maintained constant and the free hand needs to

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gather the working end to lay it down properly. Alternate loops are created either by using the forefinger or the ring and the third finger.A common mistake occurs on the recovery, when the free hand does not slide far enough up the working end and the knot is formed too close. The tension on the post should be light, but constant, to ensure the security of knots.

Another common mistake is the phenomenon that we have termed “shortening”. As learners lay down the first knot, they can pull up on the post and cinch the knot down in this way. Unfortunately as they pull the on the post, the tail becomes shorter and shorter. At the end of the first knot, the initial correct set up has completely been undermined. The post is held “high in the sky” and the tail is too short to comfortably tie. Some beginners make this mistake because they are taught to maintain tension on the post, but on the first knot, this tension is not necessary. In fact, to avoid the “shortening” of the tail, learners should avoid tension on the post until the moment the knot is laid down and being cinched. The other option is to start out with a longer tail than ideal and allow a bit of shortening. The hand holding the post can be slid down with a gathering maneuver.

Acknowledgments

The authors would like to thank Pat O’Sullivan, EdD, for her invaluable guidance in the relevant educational theory to this undertaking.

Works Cited

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Reder L, Anderson JR, and Simon HA (1996). Situated learning and education. Educational Researcher. 25(4):5-11.

Rogers DA and Ketchum J (2007). Knot Tying. In ACS/APDS Surgical Skills Curriculum for Residents: Phase1. http://elearning.facs.org/course/view.php?id=3

Rogers DA, Regehr G, and MacDonald J (2002). A role for error training in surgical technical skill instruction and evaluation. The American Journal of Surgery. 183:242-245.

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