EE WAS INSTALLING A BELT WETTER ON THE LONGWALL BELT LOCATED ON #5 HEADGATE. HE SLIPPED IN THE MUD & FELL ON HIS LEFT KNEE CAUSING IMMEDIATE PAIN. EE SOUGHT MEDICAL ATTENTION LATER & WAS ADVIS ED TO REMAIN OFF WORK. HE ALSO WAS INSTRUCTED TOBEGIN THERAPY FOR THE INJURED KNEE. SAFETY DEPT. WAS NOTIFIED THAT HE WAS OFF WORK ON 10-18-01. THIS IS AN OCCUPATIONAL INJURY.