The summer signing from Gillingham has only played a handful of games for The Lions since his arrival at The Den and is now likely to miss the rest of the season following this latest setback.
"Danny needs corrective surgery," Millwall physio Bobby Bacic told the club's official site this morning. "It has been a highly frustrating time for Danny as he managed to get about 75% fit, then the pain re-appeared. The complex nature of the problem has meant that up until now it has been very difficult to give a full diagnosis.
"We took the unorthodox step of doing a very aggressive outdoor session to flare the symptoms up so that the specialist we were seeing the next day had definite symptoms to assess.
"Danny will undergo surgery this week in Manchester which we all hope will get to the root of the problem."