Lebron James, the four-time MVP, is in danger of missing his fifth straight game Thursday with swelling in his left knee.Video of a dunk in his last game against the Nets on Jan. 25 showed concerning signs of a potential long-term issue for James.By video, James looks to have significant swelling on the back of his left knee, which the ProBasketballDocs believe is a Baker's cyst. A Baker's cyst is a fluid-filled cyst which is usually caused by arthritis or a torn meniscus in the knee.While it remains unclear exactly what the cause of the Baker's cyst is, the continued swelling is certainly not good news for James and the Lakers.James has reportedly remained in Los Angeles since Jan. 27 to undergo treatment for the knee. That treatment will not include a PRP injection, or platelet-rich plasma injection.Lakers head coach Frank Vogel said Sunday that James still had swelling in his knee and would not play until the swelling is gone.On Tuesday, Vogel said the 37-year-old's rehab was moving in the right direction.The ProBasketballDocs, Dr. David Chao and Dr. John Hefferon, say the root cause of the swelling is where the concern lies right now.The best case scenario is the swelling is related to arthritis and overuse. With this, James can return without issues as long as his minutes are managed.The worst case scenario would be a meniscus tear that requires surgery.The Lakers are 25-27 and currently sit ninth in the Western Conference.They have gone 6-10 without James this season, but now have Anthony Davis back from his left knee MCL sprain.Davis has averaged 25.3 points, 10.3 rebounds, 3 assists, 1.1 steals and 1.9 blocks in 15 games without James this season.