EMPLOYEE STATES HE WAS TIGHTENING THE NUT ON A DWYDAG BOLT WITH A JACKLEG. AS THE NUT TIGHTENED, THE JACKLEG SPUN JERKING HIS RIGHT ARM CAUSING PAIN IN HIS SHOULDER. NO REPORTABLE MEDICAL TREA TMENT WAS PROVIDED UNTIL AN MRI ON 12/1/00 INDICATED A DAMAGED ROTATOR CUFF.