I had a hen a while back, who began limping. (really couldn't put much to any weight on that leg). We really couldn't find anything wrong ( we are both registered nurses) with the leg. So we placed her in the hospital/broody cage. She seemed to slowly get better, and the cage was a see/no touch in with the other girls. After a few weeks, we went out to feed, water and let the other girls out..
When we went to feed our sick girl, she began to cry. So we decided to see what would happen if we let her out. Sure enough she ran to the rest of the flock and rejoined them without any problems.
I would put her some place safe, where she can move around if she wants, but doesn't have to, no roost bar and where she can see and interact with her flock mates for a few weeks and see how she is doing. Good Luck, I hope it is just a tendon sprain.