You can see in the  k2item.php template file that the span in itemImage has the class.

My issue was with a Joomlart.com template using the T3 framework.

Here how you can fix this K2 - boostrap conflict.

You can either:

1. Make use of your framework custom.css and add the css code below to it.
2. Create a Joomla override of the k2.css file. To do this copy k2.css from /components/com_k2/css/k2.css to your /templates/[yourtemplate]/css/k2.css

#k2Container a.modal {

display: inline-block;

position: relative;

top: auto;

left: 0px;

width: auto

}

Additionally you can make use of z-index. In my case I had an issue with the fixed menu bar having a z-index value of 100, so I adde a z-index value of 99 to the code above.