From Comcast SportsNetPHILADELPHIA (AP) -- Andrew Bynum still has pain in his left knee that has kept him from making his debut with the Philadelphia 76ers.Bynum is in pain when he walks or attempts even light physical activity, except for swimming. He had been recovering from a bone bruise in his right knee and injured his left knee while bowling last month.The 7-foot center will have his knees examined again Dec. 20th and did not know if he'd need an MRI."Worst case scenario, it's another month," he said Monday night. "Best case scenario, I can ramp it up."Bynum has not or practiced or played for the Sixers since he was acquired in the offseason from the Los Angeles Lakers. Bynum said his right knee has improved to the point where he might have been able to play. He was again listed as inactive for Philadelphia's game against Detroit with "bilateral bone bruises.""There's nothing I can do about it," he said. "It's arthritis in the knees. Cartilage is missing. That's not going to regrow itself. Maybe in the future, next three to five years, there may be something out there that really does help. Right now, it's kind of a waiting game."Bynum, 25, is in the final year of his contract and could sign a five-year deal worth more than 100 million in the offseason, if he's healthy. But his uncertain status could be costing the All-Star millions.Bynum won two NBA titles in seven seasons with the Lakers. The Sixers were hoping he could help them become one of the league's elite teams.He has tried not to think about the fact he might never play for the Sixers."I really think I'll be fine," he said. "If my left knee gets better, and feels like my right, I'll be playing."Bynum announced in May, while still a member of the Lakers, that he was going to Germany in September for the Orthokine blood-spinning treatment in his knees that other professional athletes have sought. The Sixers announced before training camp that Bynum needed to delay his return to allow the effects of the Orthokine treatment to work.The bone bruise in his right knee caused the Sixers to push the return date from training camp to the regular season and now possibly to midseason.But the Sixers are still looking long term with Bynum, who's in the last year of his contract.Bynum said the Sixers haven't really put pressure on him to return."I think initially," he said, "but then I realized more of the pressure was coming from myself. I just had to kind of relax a little bit and let this time pass."If Bynum is cleared to resume basketball activity on the 20th, he said he wouldn't need much time before he played in a game. He's become a devoted swimmer and credited that to keeping him in shape. It's one of the few activities that doesn't cause Bynum pain."It's not getting worse. It's just continuous pain," he said. "I just think the bone bruise has to heal. It's a mirror image of my right knee. My right knee took four months. I think we're a little bit ahead of the curve."