As always, your best bet is to consult with your health-care provider, who can help you diagnose and treat any knee discomfort or disfunction.
In the meantime, if you would like to learn more about healthy knee function, I recommend this article by yoga teacher Doug Keller, which explains the basics of healthy knee alignment and offers strategies for promoting knee health while practicing yoga.
Roger Cole always offers a wealth of information and inspiration, and this article on the knees is no exception. And if you still haven't had your fill, here's one last article by Catherine Guthrie. I often find relief by slipping a rolled-up washcloth into the crooks of my knees when they are bent, as described in this article.
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