My 8 year old daughter got out of a full leg cast 1 wk ago, now her knee on the same leg has fluid on it and is hurting her. could she have torn acl?

Let try to help you: Let me tell you that torn acl could happen in children but not common, and especially no trauma happened, the fluid in her knee most likely from being in the cast on for a while, you should be look at by her orthopedic surgeon. Thank you i hope she feel better.

Possibly, but rare: It is certainly possible for 8 year olds to have an acl tear, but this is quite rare. There are many more common causes of fluid in the knee after an injury such as a fracture, partial dislocation of the kneecap, cartilage tear, or bone bruise. Usually a good physical examination by an orthopedic surgeon, as well as an x-ray and possibly even an MRI will make the diagnosis.