Leamy has been dogged by the problem all season and has been limited to just seven appearances for Munster.
And the 30-year-old has been told he needs an operation to repair the damage - thus ruling him out of action for up to four months.
As a result, Munster are now weighing up bringing in a short-term replacement for their Heineken Cup squad.
"We will have to look at the numbers - we have registration to close on five or six at five o'clock on Tuesday and then we have an opportunity after that deadline if we get through to the quarter-finals," said coach Tony McGahan.
"But we still have a few guys like David Wallace and Felix Jones to come back into the squad so that immediately eats up two places already."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.