OBJECTIVE: The purpose of this study was to identify topics of potential concern to anterior cruciate ligament (ACL) surgery patients. DESIGN: An archival design was used. SETTING: Qualitative data were collected from two Internet message boards. METHOD: A thematic content analysis was performed on the initial postings of 900 threads from the archives of two online forums. Postings (N = 797) in which questions were asked of the message board communities were placed in 1 of 22 content themes by two independent raters. RESULTS: More than half of the postings in which questions were asked pertained to rehabilitation and the postoperative period (N = 436, 55%), with approximately one-third of the postings (N = 287, 36%) corresponding to issues associated with surgery and the preoperative period. The content themes observed most frequently (all with more than 51 postings) were those pertaining to rehabilitation progress, pain, complications, physical therapy, diagnosis, returning to sport, and whether to have surgery. CONCLUSIONS: A substantial number of individuals use Internet message boards to learn about ACL surgery and rehabilitation. Information gleaned from this study can be used to help ensure that the primary concerns of patients are addressed in educational materials.