Liverpool's Allen set to be sidelined for three months
The Welsh midfielder has carried the problem for most of the season and although a date for surgery has not yet been set, he has revealed that a three-month layoff is the most likely scenario once the procedure occurs.
"It requires another operation which is a bitter blow. These things happen in football, unfortunately, and it will keep me out for around three months when I do get the operation done," he told Sky Sports News.
"I'm not sure, to be honest (when the operation will be). That's something that is being decided and I will have to see what comes of it.
"I'm not looking to use it as an excuse. It's something that has deteriorated recently and it has got to a stage where an operation is all that can resolve it. I'm looking forward to getting it done, putting it behind me and moving on from there.
"It's not an ideal situation, but a player carrying an injury throughout the football season is part and parcel of the game and you come to expect it."