Commonly sprained joint (5)
I believe the answer is:
ankle
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">commonly sprained joint</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ankle that I've seen before include "Human joint" , "Joint between foot and leg" , "Location of the talus" , "Bone over foot" , "Lower leg joint" .)