EE stated that while tightening down a bolt, the wrench slipped off the bolt head causing him to strike his elbow against the side of the hopper. He stated there was no pain, no loss of motion. He was placed on modified duty. On 3-4-09, he return to the CCOM and was diagnosed with Bursitis/tendeniti/elbow soft tissue effusion which was drained from his right elbow.