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Thomas M. Krapu, Ph.D.

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A response by Dr. Tom Krapu to the article: Knee problems and the t'ai chi player, by Betsy Foster MPH (2006), published in T'ai Chi Magazine, August, 44-46. Another response by Dr. David Walls-Kaufman can be found at:

I am writing this in response to Ms. Foster's article on knee problems. There are certain problems with her article that might mislead the uninformed reader. Ms. Foster has a master's degree in public health and presents her article as a professionally written contribution to the t'ai chi community. Closer scrutiny suggests problems with the claims she makes within her article. This is unfortunate, since uninformed readers might give a greater status to her writing because of its professional appearance. This article was not published in a professional journal where it would have gone through peer review before publication. Since the readership of a consumer magazine may not have the training to evaluate this article I felt compelled to offer further perspective on her article.

One might question what my stake is in responding to Ms. Foster and what my motive is in making a public statement regarding her work so I want to discuss these issues first, before presenting my ideas about her article.

I would not be taking my own time in responding to Ms. Foster if I did not have some interest in her claim that Professor Cheng's Yang Short Form "passed on a knee disaster to us". I also feel an obligation to respond since Professor Cheng is not living to respond to her claim or correct her in a way to help her progress in her practice. I make no claim to be a Master in this art and I take responsibility for any errors or omissions of my own in this matter. The basis of my response is twofold. First, I have had instruction from several teachers who studied directly with Professor Cheng and twenty-one years of continuous practice and study of the Yang Short Form. I apologize in advance to Professor Cheng, his family and his students for any of my own misunderstandings that may occur in this response to Ms. Foster. In addition, I will conclude by responding to Ms. Foster's article based on my own training in research methodologies.

If Ms. Foster had done more research on the background of this problem and sought more qualified teachers she would have discovered other possibilities. First, a more correct practice might have eliminated her knee problem as it does for so many other t'ai chi practitioners. Secondly, she would have found that it is already common practice and "permissible" to change 90 degree single legged postures to as little as 45 degrees under special circumstances. For instance, when teaching the elderly or people with physical limitations. So her recommendation is nothing new (though she presents it as such), and is misplaced when it is suggested for all t'ai chi practitioners.

An analogy:

Imagine someone observing a yoga class. They see the most extreme yoga posture and wonder HOW this could possibly be a healthy practice. They go to a person trained in Western medicine and describe the posture. This professional, unfamiliar with yoga or misinformed themselves, makes a claim for how that posture could strain, injure, or damage the human body. They then claim that this posture and maybe even yoga in general, is dangerous and should be avoided. Again, any informed observer would know that yoga is a method of personal development and it might take years to develop the range of motion that is required by that yoga posture.

This same thing is true in the internal art of t'ai chi. People start where ever they are, in various levels of physical health. What is amazing about t'ai chi is that anyone who can walk can learn traditional t'ai chi (and there are even modified forms for wheel chairs). And the t'ai chi forms, like yoga, push our limits so there is virtually no limit to how much range of motion we can develop. But this is a gradual process that requires patient practice and proper instruction over many years.

I truly regret that Ms. Foster was plagued by knee pain in her t'ai chi development. I hope she finds the instruction she needs to correct her practice. I know that this is what Professor Cheng would want for her. I wish he were alive for us to know how he would respond. If she needs to modify the form for herself, perhaps this will be helpful in her case, but to suggest the form be changed for everyone is excessive and as Dr. David Walls-Kaufman states will, "will paint you into a range of motion corner" (2006-link).

A critique of Foster's research methodology

The second perspective that I would like to consider in evaluating her article comes more from a research design perspective and an analysis of her "anecdotal approach". I would like to address the claims and evidence that Ms. Foster presents in her article. Her claim (really a hypothesis) is that the Yang Short Form is damaging to the knee joint and the form should therefore be modified. The only evidence she presents to substantiate this claim is knee pain she herself experienced in her own personal practice. Ms. Foster does present a background to the problem, including an anatomical analysis of the knee, and testimony from others who support her claim, but then presents this background of the problem as evidence for her claim. There is circularity in this reasoning that I believe would have never been approved by a professional peer review of her article. In the research process Ms. Foster has made a statement of the problem she wants to study and formulated her hypothesis but makes claims about that hypothesis without reliably and validly testing it. This calls into question her conclusions. The evidence of HER OWN knee pain is the only evidence she offers to substantiate her claim.

There are many explanations for her knee pain other than the ones she offers. As mentioned above, her knee pain could have been caused by incorrect practice rather than any inherent problem within the Yang Short form. And this incorrect practice could be a problem regardless of what form she was practicing. In fact she as much as acknowledges this in her article when she sees the potential for her problem in other forms. Her article does not suggest that she sought a qualified teacher of the Yang Short form to help her correct her form to avoid knee pain. Rather, she assumed there was something wrong with the form, rather than her practice and then found a teacher to agree with her. This is common in my experience of this internal art, where people encounter problems in the course of their development and find the "fault" of these problems externally rather than internally. They then blame the teacher or the art for their failure rather than looking more deeply and seeking help from a qualified teacher to help them through that phase of their development in the art. Sadly, many people's development is impeded by such practices.

I would further reinforce this point by asking a simple question. If the Yang Short Form (or any other form for that matter) is inherently dangerous to the knee, then why aren't there more people with knee problems as a result of their practice? And why do so many people who study with qualified teachers not have knee problems? I believe the answer is related to the quality of the teacher and the student's practice, not the quality of the form. And I believe that this applies to all t'ai chi forms, not just the Yang Short Form.

So there is an error of logic in the article that Ms. Foster presents to the t'ai chi community. The logic goes something like this:

I have knee pain; therefore there must be something wrong with the form.
Conclusion: The form must be adapted to eliminate my knee pain.

Another analogy:

For a moment, let's imagine a Chen style t'ai chi practitioner. He or she might even be a teacher. Let's imagine that they begin to experience foot and ankle problems. Through "experimentation" they find that this problem goes away if they stop the practice of stomping their foot in their form. They begin to research the effects of "high impact" exercise and find "evidence" that high impact exercise can cause problems in the foot and ankle. Soon this teacher is "modifying" the form to protect others from hurting their feet and ankles. Any well informed t'ai chi practitioner could see the error of this thinking even if they did not practice Chen style. In truth even more absurd claims have been made about t'ai chi

I wish the best to Ms. Foster regarding her development within our art. I hope that this brief response is helpful to her as well as others who may have questions after reading her article.


Tom Krapu, PhD is a doctoral level psychologist who practices in St. Louis, Missouri, USA. He was an editorial consultant for the peer-reviewed journal Psychotherapy for twenty years where he was rated among the top 10% of editorial consultants. His background in t'ai chi can be found at:

(314) 842-2258
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Thank you for your interest.