Effusion?

Hi! About a month ago I felt a twinge pain as I was doing a lunge. Having tightness and some pain during anything weight bearing like going up stairs. Stiffness while walking. I’m also a runner. Doesn’t hurt when running. Running is a HUGE part of my mental health treatment so I haven’t given it up.

Doctor says she thinks it may be an effusion or “water on the knee.” She’s sending me for an X-ray and ultrasound.

Anyone had this before? Tips/tricks/advice?

Thank you!!