EMPLOYEE SUFFERS FROM DEGENERATIVE CONDITION OF THE LEFT KNEE WHICH CAUSES HIM PAIN FROM TIME TO TIME, ESPECIALLY WHEN HE STANDS UP FROM A KNEELING OR SQUATING POSITION. HE EXPERIENCED SUCH AN EPISODE OF PAIN WHILE ON THE JOB ON 2-16-00 WHEN HE STOOD UP FROM A KNEELING POSITION AS HE WAS TIGHTENING THE BOLTS ON THE FAN SHROUD OF O DOZER.