On 12/1/09 EE was attempting to unplug wet screen system. While standing on the screen he reported twisting his rt.knee between the spray bars. Testing diagnosed osteoarthritis until 3/5/10 arthro.exam found and repaired a torn lateral meniscus. Reportable as of 3/5/10 due to medical conf. of torn ligament not just arthritis. Temp. restrict.duty until next sch. shift.