Alec Chamberlain will take over between the sticks in Lee's absence beginning in this weekends vital away game against Rotherham.
"Everybody really feels for Richard - we just can't believe his luck," Chamberlain told the clubs official website.
"I feel desparately disappointed for him but hopefully he'll be able to get on the mend throughout the summer. It'll be a solid rehabilitation programme for him during the close-season and hopefully he can go into next year fully fit and have an injury-free year.
"I'm not a medical expert but from what the specialists have indicated, he'll have an operation very soon and the indications are that he'll be fully fit by pre-season."