Oh my goodness, I think So Yeon is injured too. I'm not a fan of reporting news, I have to share this; so here's the video of T-ara performing some songs, with So Yeon singing by the side, supported by a crutch.
She still managed to wink and smile.
And here's picture from T-araChina for a better view:
But seriously, what's with T-ara's high frequency of injuries.