EE WAS EXITING MOBILE EQUIPMENT & FELT STRAIN IN RIGHT KNEE. DID NOT REPORT IMMEDIATELY BECAUSE HE FELT IT WAS A MINOR PAIN THAT WOULD CLEAR UP. HOWEVER, INJURY CONTINUED TO HURT & PHYSICIAN P LACED HIM ON RESTRICTIONS. AREA OF ACCIDENT WAS CLEAR & FREE OF UNLEVEL SURFACES. EQUIPMENT HAD STEPS/HAND HOLDS IN GOOD CONDITION. EE IS VERY LARGE & HAS HAD PREVIOUS KNEE PROBLEMS.