The 24-year-old midfielder, who signed a new one-year deal with Dale last week, missed most of the last campaign with a shoulder problem.
Manager Keith Hill confirmed Lund may now be out of action until mid-September.
He told Dale Player: “Matty has been for a scan but the specialist hasn’t had the report at this moment in time. We’re due to get that later today (Friday) but it’s likely that it’s going to be at least four to six weeks due to the manner of the injury.
“His knee locked out and we’re waiting to see if it’s the cartilage or a small tear. The earliest we could see him back on the football pitch is mid-September.
“I’ve resigned myself to being without Matty, but there’s no panic to replace him. We could have the replacement in the building and we’ll wait to see what the next couple of games bring out.”