[header] How to confirm a partial acl tear [title] Take note if you hear a' popping' noise when the injury happens. [step] Most people state that they hear a popping noise when the acl is injured. If you heard a' popping' or' snapping' noise when you experienced your injury, it is likely that your acl has been at least partially torn. 
You should go to the doctor to get this diagnosis confirmed. [substeps] Though you will most likely be in pain, try to remember the exact sound your knee made.