EE was getting on unit #1140 end dump. The first step was high and when he pulled himself up onto the ladder he felt something pull in his right arm. Later he could not lift his arm about halfway in the air. EE worked the 17 went to Dr on 18 and was not scheduled to work that day. Not scheduled on 19 and 20 went back to Dr on 21 and released to work with no restrictions on the 22.