ACL misdiagnosis

Hi have a friend who recently has'nt played football in over a year due to a suspected ACL tear. He received an MRI scan which the radiologist said was a clean ACL tear. The scan was then read by a highly regarded Consultant who also assessed him physically and confirmed my friend's worst fears. My friend's operation was then booked after this although he then cancelled abruptly after having doubts. After partaking in a few 5 a side games with a brace he found his knee to be "better than ever" and so went for a second opinion. The second consultant who viewed his MRI and assessed him told him that his ACL was perfectly intact as was the rest of his ligaments. I still find this hard to believe because my friend would have no real reason to lie as well. So is it really a possibility that two top professionals one of those a highly regarded knee specialist both got it wrong? Also what do you think would of happened if my friend had went through with the operation??