Ok, here's how I treated the slipped tendon. By the way, that is what happened to the chick in my avatar.
Like the site says, you want to strech the chick's leg back (it may be a bit difficult) and use your fingers to gently massage the tendon back into place. It should pop back into place. After that, I take a piece of gause and wrap it around the leg. I then use a portion of a popsicle stick to keep the leg perfectly straight and use bandages or vet wrap to wrap the stick to the leg. She will not enjoy it, and she will walk funny but she needs to keep the leg straight.
I tried chick chairs, but each one was a miserable failure which is why I decided that it's better to simply keep their legs perfectly straight. The designs were good, but the chicks don't cooperate at all! They hate those chairs and will do everything in their power to get out, possibly injuring themselves further. Chick chairs look like good ideas, which is why I tried them 5 different times, but each ended up in failure.
I changed the wrapping daily because it gets dirty and you need to make sure that the tendon is still correctly positioned. I would keep it wrapped for about a week. While changing the wrapping, let the chick bend the leg if she or he chooses to do so. Just make sure the tendon is back in place before you put the wrap back on.
I have had this happen 4 different times. The first time was unsucessful, but she learned how to use her leg in a way that worked for her. She is still alive today happily hobbling around the barn eating and laying eggs just like any other chicken. I do feel bad for her though, her leg is permanently deformed and sometimes she has troubles. The reason she was unsucessful was because I was never able to get the tendon back in place. No matter how hard I tried and no matter how good I wrapped it, the tendon would be back to the side within seconds.
When another chick ended up with a slipped tendon, I followed exactly what I wrote above and he was walking normally after a week. It happned to another 2 chicks after that one and once again, both were walking normally after a week or so. It can take longer so give her time.
If you have any questions, feel free to ask.