EE REPORTS THAT CONSTANT TWISTING, TURNING & STEPPING ON TOES OF LONGWALL FACE HAS CAUSED EE'S LT. KNEE TO SWELL. WHEN HE IS REQUIRED TO WORK IN A KNEELING POSITION OR SQUATTING POSITION THE KNEE LOCKS UP & STIFFENS. ON 10/17/02 HE WENT OFF WORK FOR HIS KNEE.