'Joints' in the Bible

And a certain man drew his bow at a venture, and smote the king of Israel between the joints of the armor: wherefore he said unto the driver of his chariot, Turn thy hand, and carry me out of the host; for I am sore wounded.

And a certain man drew his bow at a venture, and smote the king of Israel between the joints of the armor: wherefore he said to the driver of the chariot, Turn thy hand, and carry me out of the host; for I am sore wounded.

Then the king's countenance was changed in him, and his thoughts troubled him; and the joints of his loins were loosed, and his knees smote one against another.