Thanks for that post. Fair point. I think in many cases the ACL undergoes repeated injury. Only perhaps a good first time injury would give the significant effusion. But who knows.

I suppose it's interesting that the Wikipedia reference-linkMRI in your case might not have provided any more assistance than the clinical observation. Thoughts? Perhaps only refer for MRI if you have the direct intention of a surgical intervention at that time. If you initial intention is conservative management then wait until that either fails or succeeds? What do you think?