While there are many ways to practice trikonasana, the usual way of transitioning into it is with the front leg already straight. There's nothing inherently wrong with this approach, if a) your students have relatively flexible hamstrings and b) they have the body awareness and physical ability to laterally tilt their pelvis. However, what often seems to happen is that many students have difficulty laterally tilting their pelvis for one of the above reasons and as a result end up laterally flexing their waist in order to get their hand down to their shin bone or a block. So they end up looking more like the student in Figure A than the student in Figure B.
Part 1 of this 2-part post includes a discussion with images illustrating a unique way of transitioning into trikonasana that makes it easier for some students to finesse the perfect amount of hamstring stretch while maintaining strong lines of energy through the axial body and extremities. Part 2 is a 5-minute video that shows these steps, along with a couple of hands-on assists that accompany them. Enjoy!
Do you still practice and teach revolved triangle? I was reading through a thread in one of the Facebook forums that I belong to, and a lot of yoga teachers were saying that they no longer practice or teach this pose for a variety of reasons. Some people stated that they just didn't understand it enough to teach it. Others felt like it caused a bit of stress to their SI joints, or they just felt awkward and uncomfortable in the pose and so were concerned about teaching it to their students. One teacher expressed frustration that students in her classes would often choose not to place their hand on a block, even though she could see that the trunk flexion caused by placing the hand on the floor was clearly inhibiting their ability to rotate their trunk.
When I was a relatively new yoga student I remember expressing my strong dislike of revolved triangle to one of my teachers, and she said to me: "Your mission, if you choose to accept it, is to find a way to fall in love with this pose. You can use whatever props you like." I took her up on the challenge, and ended up finding a way to do it with my forearm propped up on the kitchen table that actually felt somewhat enjoyable. And today it's one of my favorite postures.
If you dislike revolved triangle, or find it somewhat difficult to teach, check out the above video that Frances and I created to show a step-by-step progression into the pose that might help you and your students experience a little more ease and joy. One of the key teaching points is to facilitate more spinal rotation by preserving the lift of the chest and extension of the spine throughout the pose by: