Knee joint effusion

I had an MRI to evaluate anteromedial knee pain which I posted about here previously.  ACL is intact.  I do have a joint effusion and some changes to my lateral meniscus.  I have been taking Naproxen 550mg twice a day and have had a IM steroid injection with minor improvement in the pain.  Nothing showed in the MRI that would indicate the cause of the pain where I am feeling it.  Can a knee joint effusion be present for no reason, and can it cause a great deal of pain?  I don't see my surgeon for another 3 weeks.  Thank you.

[Michael L Gross, MD]

Effusions are usually a reaction to a problem, not the problem itself. Similar to a sneeze. Sometimes they can be a result of local inflammation which can be resolved with the treatment you have had so far. Its possible that the "changes" to the lateral meniscus represent a tear, and that could be the cause of the persistant effusion.