Employee was assigned the job of changing out a blown hydraulic hose located below the hitch on a haul truck. As he was positioning himself below the hitch, his left foot slipped and he twisted his left knee. The employee was diagnosed with a torn medial meniscus of his left knee on 4/2/08. He worked regular duty until his knee surgery on 5/9/08-returned to full duty on 6/16/08-