EE was installing bent plate around screens in a kneeling position. Whe he stood up he experienced a catch in his right knee, causing pain & the inability to straighten it. EE missed 5/7 & 5/8 and 6/14 - 7/5/07 for knee surgery. This office notified of surgery and lost days 10/23/07. (addition to narrative per MM 10/26/07 #10)