Knee pain on outer part of knee. What can it be? Two months ago, I injured my left knee playing tennis. The most significant symptom is that it hurts on the outside of the knee when I squat or go down a flight of stairs. Also, when I'm going downhill. According to my orthopedist (who saw the MRI but not the radiologist reading), I have a lateral meniscus tear. I got an MRI and the reading says the following. The problem is that my lateral meniscus is intact. The x-rays are also negative. So where is the pain coming from? IMPRESSION: 1. Moderate size joint effusion with small subchondral irregularity of the posterior and superior patella. Correlate clinically. 2. Oblique tear of posterior horn medial meniscus with sprain of the ACL. 3, myxoid degeneration in the posterior horn of the lateral meniscus. The reason I don't go to the ortho again is because he suggested arthroscopic surgery without actually being certain of what I have. Plus, he said I had a tear in the lateral meniscus, but that meniscus is fine. Since my lateral meniscus is fine, what can the problem be? I don't have any symptoms of an injury in the medial meniscus.