http://helloproject.com/news/9669/
Nakanishi Kana has a problem with her left Achilles tendon and has to rest for 4 ~ 6 weeks at least. She will participate seated at Angerme's Christmas event, will miss Angerme performance at rock'on Countdown and will only do MC for H!P Countdown and Tokyo dates on the winter tour. She should take part to the rest of Angerme's activities, as long as she doesn't have difficulties to do so. They will see if she feels better in the course of January, if her medical treatment goes well, and decide what to do next around that time.
Edit : Here is 910 percent (on Facebook) translation of the first part of the official announcement.
Thanks for supporting Hello! Project as always.
Nakanishi Kana has a pain on her leg since the middle of last month.
We consulted our physician and had watched over her.
but he didn't recover.
He feels pain even when she just walk.
She had a detailed examination again.
She was diagnosed with Achilles Tendon Enthesitis
According to the doctor, It requires medical treatment with rest for four or six weeks.
from Meikochi of mmbbs