Depends on how your league handles injured players. Mine has the following rules:
To trade an injured player: the person giving the injured player must announce tehat the player is injured on the discussion board, with any pertinent information regarding the nature of injury and expected down time. The person receiving the injured player, must acknowledge that the player is injured on the messge board. Otherwise the trade is not permitted.
If a player is injured while a trade is being processed, the trade goes through as normal, as the trade was agreed to without injury.