Let's concentrate on the legs and knees. When I watch my students, I often see a fair amount of confusion as to how far to step and how far to extend the knee in relation to its foot's placement. I have talked a little bit about how to place one's feet in relation to each other so let's focus first on how far you should step.
What I teach is that it is totally unique to each individual. Tall people with long legs are often going to step out further than a short person like myself. The bottom line is that there is no simple formula for distance that I know of. It also depends on what you are practicing at a given moment. Often, when I do a form in the morning, I'm still a little stiff and so I tend to economize in movement - all my movements - but especially the extensions. In the afternoon and evenings, I'm a lot looser so I will often explore larger movements and leg extensions. That translates into needing anywhere from 1/3 to 1/2 the space to do the same form in the morning vs the evening! And I'll sink lower later in the day, which also makes it easier to do longer extensions, especially in Chen forms.
Ok, how about the knees. I have only one critical rule for your knees and it's this:
- Never let your front knee extend past the toes of its foot!!
- Repeat, Never let your front knee extend past the toes of its foot.
Let's take a look at a picture taken from this article about Tai Chi's effectiveness for increasing motion in arthritic joints. Look particularly at the top right and lower left drawings. This has the angle where the leg meets the foot looking like the corner of a square when viewed from the side. This is the most comfortable, least stressful position for the joints, will result in smoother form work, and facilitates sending your Chi energy into the earth through the heel and bubbling well to establish your root.
Also note that the upper body has the spine at a right angle to the ground, as well. This prevents you from overextending your arms and helps to establish a good sense of balance and rooting.
So if you haven't thought much about it, this is a good time to examine how you're positioning your body in regard to these basic concepts. And keep practicing!! A little effort each day can take you a long way on this T'ai Chi journey you're on.